Add @Nullable and @NonNull annotations

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -722,7 +722,7 @@ public class ComputerCraft
         }
     }
 
-    public static IMount createResourceMount( Class modClass, String domain, String subPath )
+    public static IMount createResourceMount( Class<?> modClass, String domain, String subPath )
     {
         // Start building list of mounts
         List<IMount> mounts = new ArrayList<IMount>();
@@ -806,7 +806,7 @@ public class ComputerCraft
         }
     }
 
-    private static File getContainingJar( Class modClass )
+    private static File getContainingJar( Class<?> modClass )
     {
         String path = modClass.getProtectionDomain().getCodeSource().getLocation().getPath();
         int bangIndex = path.indexOf( "!" );
@@ -831,7 +831,7 @@ public class ComputerCraft
         return file;
     }
 
-    private static File getDebugCodeDir( Class modClass )
+    private static File getDebugCodeDir( Class<?> modClass )
     {
         String path = modClass.getProtectionDomain().getCodeSource().getLocation().getPath();
         int bangIndex = path.indexOf("!");

src/main/java/dan200/computercraft/api/ComputerCraftAPI.java

@@ -21,6 +21,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.lang.reflect.Method;
 
 /**
@@ -36,6 +38,7 @@ public final class ComputerCraftAPI
         return computerCraft != null;
     }
 
+    @Nonnull
     public static String getInstalledVersion()
     {
         findCC();
@@ -50,6 +53,7 @@ public final class ComputerCraftAPI
         return "";
     }
 
+    @Nonnull
     public static String getAPIVersion()
     {
         return "${version}";
@@ -68,7 +72,7 @@ public final class ComputerCraftAPI
      * available for writing.
      * @see #createSaveDirMount(World, String, long)
      */
-    public static int createUniqueNumberedSaveDir( World world, String parentSubPath )
+    public static int createUniqueNumberedSaveDir( @Nonnull World world, @Nonnull String parentSubPath )
     {
         findCC();
         if( computerCraft_createUniqueNumberedSaveDir != null )
@@ -100,7 +104,8 @@ public final class ComputerCraftAPI
      * @see IMount
      * @see IWritableMount
      */
-    public static IWritableMount createSaveDirMount( World world, String subPath, long capacity )
+    @Nullable
+    public static IWritableMount createSaveDirMount( @Nonnull World world, @Nonnull String subPath, long capacity )
     {
         findCC();
         if( computerCraft_createSaveDirMount != null )
@@ -132,7 +137,8 @@ public final class ComputerCraftAPI
      * @see IComputerAccess#mountWritable(String, IWritableMount)
      * @see IMount
      */
-    public static IMount createResourceMount( Class modClass, String domain, String subPath )
+    @Nullable
+    public static IMount createResourceMount( @Nonnull Class<?> modClass, @Nonnull String domain, @Nonnull String subPath )
     {
         findCC();
         if( computerCraft_createResourceMount != null )
@@ -153,7 +159,7 @@ public final class ComputerCraftAPI
      * @see dan200.computercraft.api.peripheral.IPeripheral
      * @see dan200.computercraft.api.peripheral.IPeripheralProvider
      */
-    public static void registerPeripheralProvider( IPeripheralProvider handler )
+    public static void registerPeripheralProvider( @Nonnull IPeripheralProvider handler )
     {
         findCC();
         if ( computerCraft_registerPeripheralProvider != null)
@@ -174,7 +180,7 @@ public final class ComputerCraftAPI
      * @param upgrade The turtle upgrade to register.
      * @see dan200.computercraft.api.turtle.ITurtleUpgrade
      */
-    public static void registerTurtleUpgrade( ITurtleUpgrade upgrade )
+    public static void registerTurtleUpgrade( @Nonnull ITurtleUpgrade upgrade )
     {
         if( upgrade != null )
         {
@@ -196,7 +202,7 @@ public final class ComputerCraftAPI
      * @param handler The bundled redstone provider to register.
      * @see dan200.computercraft.api.redstone.IBundledRedstoneProvider
      */
-    public static void registerBundledRedstoneProvider( IBundledRedstoneProvider handler )
+    public static void registerBundledRedstoneProvider( @Nonnull IBundledRedstoneProvider handler )
     {
         findCC();
         if( computerCraft_registerBundledRedstoneProvider != null )
@@ -219,7 +225,7 @@ public final class ComputerCraftAPI
      * If there is no block capable of emitting bundled redstone at the location, -1 will be returned.
      * @see dan200.computercraft.api.redstone.IBundledRedstoneProvider
      */
-    public static int getBundledRedstoneOutput( World world, BlockPos pos, EnumFacing side )
+    public static int getBundledRedstoneOutput( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side )
     {
         findCC();
         if( computerCraft_getDefaultBundledRedstoneOutput != null )
@@ -239,7 +245,7 @@ public final class ComputerCraftAPI
      * @param handler The media provider to register.
      * @see dan200.computercraft.api.media.IMediaProvider
      */
-    public static void registerMediaProvider( IMediaProvider handler )
+    public static void registerMediaProvider( @Nonnull IMediaProvider handler )
     {
         findCC();
         if( computerCraft_registerMediaProvider != null )
@@ -258,7 +264,7 @@ public final class ComputerCraftAPI
      * @param handler The turtle permission provider to register.
      * @see dan200.computercraft.api.permissions.ITurtlePermissionProvider
      */
-    public static void registerPermissionProvider( ITurtlePermissionProvider handler )
+    public static void registerPermissionProvider( @Nonnull ITurtlePermissionProvider handler )
     {
         findCC();
         if( computerCraft_registerPermissionProvider != null )
@@ -271,7 +277,8 @@ public final class ComputerCraftAPI
         }
     }
 
-    public static void registerPocketUpgrade(IPocketUpgrade upgrade) {
+    public static void registerPocketUpgrade( @Nonnull IPocketUpgrade upgrade )
+    {
         findCC();
         if(computerCraft_registerPocketUpgrade != null) {
             try {
@@ -331,7 +338,7 @@ public final class ComputerCraftAPI
         }
     }
 
-    private static Method findCCMethod( String name, Class[] args )
+    private static Method findCCMethod( String name, Class<?>[] args )
     {
         try {
             if( computerCraft != null )

src/main/java/dan200/computercraft/api/filesystem/IMount.java

@@ -10,6 +10,7 @@ import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
@@ -36,7 +37,7 @@ public interface IMount
      * @return If the file exists.
      * @throws IOException If an error occurs when checking the existence of the file.
      */
-    public boolean exists( String path ) throws IOException;
+    boolean exists( @Nonnull String path ) throws IOException;
 
     /**
      * Returns whether a file with a given path is a directory or not.
@@ -45,7 +46,7 @@ public interface IMount
      * @return If the file exists and is a directory
      * @throws IOException If an error occurs when checking whether the file is a directory.
      */
-    public boolean isDirectory( String path ) throws IOException;
+    boolean isDirectory( @Nonnull String path ) throws IOException;
 
     /**
      * Returns the file names of all the files in a directory.
@@ -54,7 +55,7 @@ public interface IMount
      * @param contents A list of strings. Add all the file names to this list.
      * @throws IOException If the file was not a directory, or could not be listed.
      */
-    public void list( String path, List<String> contents ) throws IOException;
+    void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException;
 
     /**
      * Returns the size of a file with a given path, in bytes
@@ -63,7 +64,7 @@ public interface IMount
      * @return The size of the file, in bytes.
      * @throws IOException If the file does not exist, or its size could not be determined.
      */
-    public long getSize( String path ) throws IOException;
+    long getSize( @Nonnull String path ) throws IOException;
 
     /**
      * Opens a file with a given path, and returns an {@link InputStream} representing its contents.
@@ -72,5 +73,6 @@ public interface IMount
      * @return A stream representing the contents of the file.
      * @throws IOException If the file does not exist, or could not be opened.
      */
-    public InputStream openForRead( String path ) throws IOException;
+    @Nonnull
+    InputStream openForRead( @Nonnull String path ) throws IOException;
 }

src/main/java/dan200/computercraft/api/filesystem/IWritableMount.java

@@ -10,6 +10,7 @@ import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.OutputStream;
 
@@ -33,7 +34,7 @@ public interface IWritableMount extends IMount
      * @param path A file path in normalised format, relative to the mount location. ie: "programs/mynewprograms".
      * @throws IOException If the directory already exists or could not be created.
      */
-    public void makeDirectory( String path ) throws IOException;
+    void makeDirectory( @Nonnull String path ) throws IOException;
 
     /**
      * Deletes a directory at a given path inside the virtual file system.
@@ -41,7 +42,7 @@ public interface IWritableMount extends IMount
      * @param path A file path in normalised format, relative to the mount location. ie: "programs/myoldprograms".
      * @throws IOException If the file does not exist or could not be deleted.
      */
-    public void delete( String path ) throws IOException;
+    void delete( @Nonnull String path ) throws IOException;
 
     /**
      * Opens a file with a given path, and returns an {@link OutputStream} for writing to it.
@@ -50,7 +51,8 @@ public interface IWritableMount extends IMount
      * @return A stream for writing to
      * @throws IOException If the file could not be opened for writing.
      */
-    public OutputStream openForWrite( String path ) throws IOException;
+    @Nonnull
+    OutputStream openForWrite( @Nonnull String path ) throws IOException;
 
     /**
      * Opens a file with a given path, and returns an {@link OutputStream} for appending to it.
@@ -59,7 +61,8 @@ public interface IWritableMount extends IMount
      * @return A stream for writing to.
      * @throws IOException If the file could not be opened for writing.
      */
-    public OutputStream openForAppend( String path ) throws IOException;
+    @Nonnull
+    OutputStream openForAppend( @Nonnull String path ) throws IOException;
 
     /**
      * Get the amount of free space on the mount, in bytes. You should decrease this value as the user writes to the
@@ -68,5 +71,5 @@ public interface IWritableMount extends IMount
      * @return The amount of free space, in bytes.
      * @throws IOException If the remaining space could not be computed.
      */
-    public long getRemainingSpace() throws IOException;
+    long getRemainingSpace() throws IOException;
 }

src/main/java/dan200/computercraft/api/lua/ILuaContext.java

@@ -6,6 +6,9 @@
 
 package dan200.computercraft.api.lua;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * An interface passed to peripherals and {@link ILuaObject}s by computers or turtles, providing methods
  * that allow the peripheral call to wait for events before returning, just like in lua. This is very useful if you need
@@ -28,7 +31,8 @@ public interface ILuaContext
      *                              event, InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      */
-    public Object[] pullEvent( String filter ) throws LuaException, InterruptedException;
+    @Nonnull
+    Object[] pullEvent( @Nullable String filter ) throws LuaException, InterruptedException;
 
     /**
      * The same as {@link #pullEvent(String)}, except "terminated" events are ignored. Only use this if you want to
@@ -42,7 +46,8 @@ public interface ILuaContext
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #pullEvent(String)
      */
-    public Object[] pullEventRaw( String filter ) throws InterruptedException;
+    @Nonnull
+    Object[] pullEventRaw( @Nullable String filter ) throws InterruptedException;
 
     /**
      * Yield the current coroutine with some arguments until it is resumed. This method is exactly equivalent to
@@ -55,7 +60,8 @@ public interface ILuaContext
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #pullEvent(String)
      */
-    public Object[] yield( Object[] arguments ) throws InterruptedException;
+    @Nonnull
+    Object[] yield( @Nullable Object[] arguments ) throws InterruptedException;
 
     /**
      * Queue a task to be executed on the main server thread at the beginning of next tick, waiting for it to complete.
@@ -71,7 +77,8 @@ public interface ILuaContext
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      */
-    public Object[] executeMainThreadTask( ILuaTask task ) throws LuaException, InterruptedException;
+    @Nullable
+    Object[] executeMainThreadTask( @Nonnull ILuaTask task ) throws LuaException, InterruptedException;
 
     /**
      * Queue a task to be executed on the main server thread at the beginning of next tick, but do not wait for it to
@@ -86,5 +93,5 @@ public interface ILuaContext
      * @return The "id" of the task. This will be the first argument to the {@code task_completed} event.
      * @throws LuaException If the task could not be queued.
      */
-    public long issueMainThreadTask( ILuaTask task ) throws LuaException;
+    long issueMainThreadTask( @Nonnull ILuaTask task ) throws LuaException;
 }

src/main/java/dan200/computercraft/api/lua/ILuaObject.java

@@ -9,6 +9,9 @@ package dan200.computercraft.api.lua;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * An interface for representing custom objects returned by {@link IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])}
  * calls.
@@ -24,7 +27,8 @@ public interface ILuaObject
      * @return The method names this object provides.
      * @see IPeripheral#getMethodNames()
      */
-    public String[] getMethodNames();
+    @Nonnull
+    String[] getMethodNames();
 
     /**
      * Called when a user calls one of the methods that this object implements. This works the same as
@@ -47,5 +51,6 @@ public interface ILuaObject
      *                              intercepted, or the computer will leak memory and end up in a broken state.w
      * @see IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])
      */
-    public Object[] callMethod( ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException;
+    @Nullable
+    Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException;
 }

src/main/java/dan200/computercraft/api/lua/ILuaTask.java

@@ -6,6 +6,8 @@
 
 package dan200.computercraft.api.lua;
 
+import javax.annotation.Nullable;
+
 /**
  * A task which can be executed via {@link ILuaContext#executeMainThreadTask(ILuaTask)} or
  * {@link ILuaContext#issueMainThreadTask(ILuaTask)}. This will be run on the main thread, at the beginning of the
@@ -25,5 +27,6 @@ public interface ILuaTask
      *                      same message as your exception. Use this to throw appropriate errors if the wrong
      *                      arguments are supplied to your method.
      */
-    public Object[] execute() throws LuaException;
+    @Nullable
+    Object[] execute() throws LuaException;
 }

src/main/java/dan200/computercraft/api/lua/LuaException.java

@@ -6,6 +6,8 @@
 
 package dan200.computercraft.api.lua;
 
+import javax.annotation.Nullable;
+
 /**
  * An exception representing an error in Lua, like that raised by the {@code error()} function.
  */
@@ -19,12 +21,12 @@ public class LuaException extends Exception
         this( "error", 1 );
     }
 
-    public LuaException( String message )
+    public LuaException( @Nullable String message )
     {
         this( message, 1 );
     }
 
-    public LuaException( String message, int level )
+    public LuaException( @Nullable String message, int level )
     {
         super( message );
         m_level = level;

src/main/java/dan200/computercraft/api/media/IMedia.java

@@ -11,6 +11,9 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * Represents an item that can be placed in a disk drive and used by a Computer.
  * Implement this interface on your Item class to allow it to be used in the drive.
@@ -23,7 +26,8 @@ public interface IMedia
      * @param stack The itemstack to inspect.
      * @return The label. ie: "Dan's Programs".
      */
-    public String getLabel( ItemStack stack );
+    @Nullable
+    String getLabel( @Nonnull ItemStack stack );
 
     /**
      * Set a string representing the label of this item. Will be called vi {@code disk.setLabel()} in lua.
@@ -32,7 +36,7 @@ public interface IMedia
      * @param label The string to set the label to.
      * @return true if the label was updated, false if the label may not be modified.
      */
-    public boolean setLabel( ItemStack stack, String label );
+    boolean setLabel( @Nonnull ItemStack stack, @Nullable String label );
 
     /**
      * If this disk represents an item with audio (like a record), get the readable name of the audio track. ie:
@@ -41,7 +45,8 @@ public interface IMedia
      * @param stack The itemstack to inspect.
      * @return The name, or null if this item does not represent an item with audio.
      */
-    public String getAudioTitle( ItemStack stack );
+    @Nullable
+    String getAudioTitle( @Nonnull ItemStack stack );
 
     /**
      * If this disk represents an item with audio (like a record), get the resource name of the audio track to play.
@@ -49,7 +54,8 @@ public interface IMedia
      * @param stack The itemstack to inspect.
      * @return The name, or null if this item does not represent an item with audio.
      */
-    public SoundEvent getAudio( ItemStack stack );
+    @Nullable
+    SoundEvent getAudio( @Nonnull ItemStack stack );
 
     /**
      * If this disk represents an item with data (like a floppy disk), get a mount representing it's contents. This will
@@ -64,5 +70,6 @@ public interface IMedia
      * @see dan200.computercraft.api.ComputerCraftAPI#createSaveDirMount(World, String, long)
      * @see dan200.computercraft.api.ComputerCraftAPI#createResourceMount(Class, String, String)
      */
-    public IMount createDataMount( ItemStack stack, World world );
+    @Nullable
+    IMount createDataMount( @Nonnull ItemStack stack, @Nonnull World world );
 }

src/main/java/dan200/computercraft/api/media/IMediaProvider.java

@@ -8,6 +8,9 @@ package dan200.computercraft.api.media;
 
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * This interface is used to provide {@link IMedia} implementations for {@link ItemStack}.
  *
@@ -22,5 +25,6 @@ public interface IMediaProvider
      * @return An IMedia implementation, or null if the item is not something you wish to handle
      * @see dan200.computercraft.api.ComputerCraftAPI#registerMediaProvider(IMediaProvider)
      */
-    public IMedia getMedia( ItemStack stack );
+    @Nullable
+    IMedia getMedia( @Nonnull ItemStack stack );
 }

src/main/java/dan200/computercraft/api/peripheral/IComputerAccess.java

@@ -11,6 +11,9 @@ import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * The interface passed to peripherals by computers or turtles, providing methods
  * that they can call. This should not be implemented by your classes. Do not interact
@@ -33,7 +36,8 @@ public interface IComputerAccess
      * @see #unmount(String)
      * @see IMount
      */
-    public String mount( String desiredLocation, IMount mount );
+    @Nullable
+    String mount( @Nonnull String desiredLocation, @Nonnull IMount mount );
 
     /**
      * Mount a mount onto the computer's file system in a read only mode.
@@ -51,7 +55,8 @@ public interface IComputerAccess
      * @see #unmount(String)
      * @see IMount
      */
-    public String mount( String desiredLocation, IMount mount, String driveName );
+    @Nullable
+    String mount( @Nonnull String desiredLocation, @Nonnull IMount mount, @Nonnull String driveName );
 
     /**
      * Mount a mount onto the computer's file system in a writable mode.
@@ -67,7 +72,8 @@ public interface IComputerAccess
      * @see #unmount(String)
      * @see IMount
      */
-    public String mountWritable( String desiredLocation, IWritableMount mount );
+    @Nullable
+    String mountWritable( @Nonnull String desiredLocation, @Nonnull IWritableMount mount );
 
     /**
      * Mount a mount onto the computer's file system in a writable mode.
@@ -84,7 +90,7 @@ public interface IComputerAccess
      * @see #unmount(String)
      * @see IMount
      */
-    public String mountWritable( String desiredLocation, IWritableMount mount, String driveName );
+    String mountWritable( @Nonnull String desiredLocation, @Nonnull IWritableMount mount, @Nonnull String driveName );
 
     /**
      * Unmounts a directory previously mounted onto the computers file system by {@link #mount(String, IMount)}
@@ -104,7 +110,7 @@ public interface IComputerAccess
      * @see #mount(String, IMount)
      * @see #mountWritable(String, IWritableMount)
      */
-    public void unmount( String location );
+    void unmount( @Nullable String location );
 
     /**
      * Returns the numerical ID of this computer.
@@ -114,7 +120,7 @@ public interface IComputerAccess
      *
      * @return The identifier.
      */
-    public int getID();
+    int getID();
 
     /**
      * Causes an event to be raised on this computer, which the computer can respond to by calling
@@ -134,7 +140,7 @@ public interface IComputerAccess
      * @throws RuntimeException If the peripheral has been detached.
      * @see dan200.computercraft.api.peripheral.IPeripheral#callMethod
      */
-    public void queueEvent( String event, Object[] arguments );
+    void queueEvent( @Nonnull String event, @Nullable Object[] arguments );
 
     /**
      * Get a string, unique to the computer, by which the computer refers to this peripheral.
@@ -146,5 +152,6 @@ public interface IComputerAccess
      * @return A string unique to the computer, but not globally.
      * @throws RuntimeException If the peripheral has been detached.
      */
-    public String getAttachmentName();
+    @Nonnull
+    String getAttachmentName();
 }

src/main/java/dan200/computercraft/api/peripheral/IPeripheral.java

@@ -9,6 +9,9 @@ package dan200.computercraft.api.peripheral;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * The interface that defines a peripheral. See {@link IPeripheralProvider} for how to associate blocks with peripherals.
  */
@@ -20,7 +23,8 @@ public interface IPeripheral
      *
      * @return A string identifying the type of peripheral.
      */
-    public String getType();
+    @Nonnull
+    String getType();
 
     /**
      * Should return an array of strings that identify the methods that this
@@ -30,7 +34,8 @@ public interface IPeripheral
      * @return An array of strings representing method names.
      * @see #callMethod
      */
-    public String[] getMethodNames();
+    @Nonnull
+    String[] getMethodNames();
 
     /**
      * This is called when a lua program on an attached computer calls {@code peripheral.call()} with
@@ -66,7 +71,8 @@ public interface IPeripheral
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #getMethodNames
      */
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException;
+    @Nullable
+    Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException;
 
     /**
      * Is called when canAttachToSide has returned true, and a computer is attaching to the peripheral.
@@ -85,7 +91,7 @@ public interface IPeripheral
      *                 computers can be attached to a peripheral at once.
      * @see #detach
      */
-    public void attach( IComputerAccess computer );
+    void attach( @Nonnull IComputerAccess computer );
 
     /**
      * Is called when a computer is detaching from the peripheral.
@@ -102,7 +108,7 @@ public interface IPeripheral
      *                 computers can be attached to a peripheral at once.
      * @see #detach
      */
-    public void detach( IComputerAccess computer );
+    void detach( @Nonnull IComputerAccess computer );
 
     /**
      * Determine whether this peripheral is equivalent to another one.
@@ -113,5 +119,5 @@ public interface IPeripheral
      * @param other The peripheral to compare against. This may be {@code null}.
      * @return Whether these peripherals are equivalent.
      */
-    public boolean equals( IPeripheral other );
+    boolean equals( @Nullable IPeripheral other );
 }

src/main/java/dan200/computercraft/api/peripheral/IPeripheralProvider.java

@@ -10,6 +10,9 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * This interface is used to create peripheral implementations for blocks.
  *
@@ -26,5 +29,6 @@ public interface IPeripheralProvider
      * @return A peripheral, or {@code null} if there is not a peripheral here you'd like to handle.
      * @see dan200.computercraft.api.ComputerCraftAPI#registerPeripheralProvider(IPeripheralProvider)
      */
-    public IPeripheral getPeripheral( World world, BlockPos pos, EnumFacing side );
+    @Nullable
+    IPeripheral getPeripheral( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side );
 }

src/main/java/dan200/computercraft/api/permissions/ITurtlePermissionProvider.java

@@ -9,6 +9,8 @@ package dan200.computercraft.api.permissions;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 /**
  * This interface is used to restrict where turtles can move or build.
  *
@@ -25,7 +27,7 @@ public interface ITurtlePermissionProvider
      * @param pos   The location of the block.
      * @return Whether the turtle can move into this block.
      */
-    public boolean isBlockEnterable( World world, BlockPos pos );
+    boolean isBlockEnterable( @Nonnull World world, @Nonnull BlockPos pos );
 
     /**
      * Determine whether a block can be modified by a turtle.
@@ -36,5 +38,5 @@ public interface ITurtlePermissionProvider
      * @param pos   The location of the block.
      * @return Whether the turtle can modify this block.
      */
-    public boolean isBlockEditable( World world, BlockPos pos );
+    boolean isBlockEditable( @Nonnull World world, @Nonnull BlockPos pos );
 }

src/main/java/dan200/computercraft/api/redstone/IBundledRedstoneProvider.java

@@ -10,6 +10,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 /**
  * This interface is used to provide bundled redstone output for blocks.
  *
@@ -27,5 +29,5 @@ public interface IBundledRedstoneProvider
      * handle this block.
      * @see dan200.computercraft.api.ComputerCraftAPI#registerBundledRedstoneProvider(IBundledRedstoneProvider)
      */
-    public int getBundledRedstoneOutput( World world, BlockPos pos, EnumFacing side );
+    int getBundledRedstoneOutput( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side );
 }

src/main/java/dan200/computercraft/api/turtle/ITurtleAccess.java

@@ -16,6 +16,9 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * The interface passed to turtle by turtles, providing methods that they can call.
  *
@@ -29,14 +32,16 @@ public interface ITurtleAccess
      *
      * @return the world in which the turtle resides.
      */
-    public World getWorld();
+    @Nonnull
+    World getWorld();
 
     /**
      * Returns a vector containing the integer co-ordinates at which the turtle resides.
      *
      * @return a vector containing the integer co-ordinates at which the turtle resides.
      */
-    public BlockPos getPosition();
+    @Nonnull
+    BlockPos getPosition();
 
     /**
      * Attempt to move this turtle to a new position.
@@ -51,7 +56,7 @@ public interface ITurtleAccess
      * {@link dan200.computercraft.api.permissions.ITurtlePermissionProvider#isBlockEnterable(World, BlockPos)}.
      * @throws UnsupportedOperationException When attempting to teleport on the client side.
      */
-    public boolean teleportTo( World world, BlockPos pos );
+    boolean teleportTo( @Nonnull World world, @Nonnull BlockPos pos );
 
     /**
      * Returns a vector containing the floating point co-ordinates at which the turtle is rendered.
@@ -61,7 +66,8 @@ public interface ITurtleAccess
      * @return A vector containing the floating point co-ordinates at which the turtle resides.
      * @see #getVisualYaw(float)
      */
-    public Vec3d getVisualPosition( float f );
+    @Nonnull
+    Vec3d getVisualPosition( float f );
 
     /**
      * Returns the yaw the turtle is facing when it is rendered.
@@ -70,7 +76,7 @@ public interface ITurtleAccess
      * @return The yaw the turtle is facing.
      * @see #getVisualPosition(float)
      */
-    public float getVisualYaw( float f );
+    float getVisualYaw( float f );
 
     /**
      * Returns the world direction the turtle is currently facing.
@@ -78,7 +84,8 @@ public interface ITurtleAccess
      * @return The world direction the turtle is currently facing.
      * @see #setDirection(EnumFacing)
      */
-    public EnumFacing getDirection();
+    @Nonnull
+    EnumFacing getDirection();
 
     /**
      * Set the direction the turtle is facing. Note that this will not play a rotation animation, you will also need to
@@ -87,7 +94,7 @@ public interface ITurtleAccess
      * @param dir The new direction to set. This should be on either the x or z axis (so north, south, east or west).
      * @see #getDirection()
      */
-    public void setDirection( EnumFacing dir );
+    void setDirection( @Nonnull EnumFacing dir );
 
     /**
      * Get the currently selected slot in the turtle's inventory.
@@ -96,7 +103,7 @@ public interface ITurtleAccess
      * @see #getInventory()
      * @see #setSelectedSlot(int)
      */
-    public int getSelectedSlot();
+    int getSelectedSlot();
 
     /**
      * Set the currently selected slot in the turtle's inventory.
@@ -107,7 +114,7 @@ public interface ITurtleAccess
      * @see #getInventory()
      * @see #getSelectedSlot()
      */
-    public void setSelectedSlot( int slot );
+    void setSelectedSlot( int slot );
 
     /**
      * Sets the colour of the turtle, as if the player had dyed it with a dye item.
@@ -116,7 +123,7 @@ public interface ITurtleAccess
      *                  the dye from the turtle.
      * @see #getDyeColour()
      */
-    public void setDyeColour( int dyeColour );
+    void setDyeColour( int dyeColour );
 
     /**
      * Gets the colour the turtle has been dyed.
@@ -125,14 +132,15 @@ public interface ITurtleAccess
      * is clean.
      * @see #getDyeColour()
      */
-    public int getDyeColour();
+    int getDyeColour();
 
     /**
      * Get the inventory of this turtle
      *
      * @return This turtle's inventory
      */
-    public IInventory getInventory();
+    @Nonnull
+    IInventory getInventory();
 
     /**
      * Determine whether this turtle will require fuel when performing actions.
@@ -141,7 +149,7 @@ public interface ITurtleAccess
      * @see #getFuelLevel()
      * @see #setFuelLevel(int)
      */
-    public boolean isFuelNeeded();
+    boolean isFuelNeeded();
 
     /**
      * Get the current fuel level of this turtle.
@@ -150,7 +158,7 @@ public interface ITurtleAccess
      * @see #isFuelNeeded()
      * @see #setFuelLevel(int)
      */
-    public int getFuelLevel();
+    int getFuelLevel();
 
     /**
      * Set the fuel level to a new value. It is generally preferred to use {@link #consumeFuel(int)}} or {@link #addFuel(int)}
@@ -162,14 +170,14 @@ public interface ITurtleAccess
      * @see #addFuel(int)
      * @see #consumeFuel(int)
      */
-    public void setFuelLevel( int fuel );
+    void setFuelLevel( int fuel );
 
     /**
      * Get the maximum amount of fuel a turtle can hold.
      *
      * @return The turtle's fuel limit.
      */
-    public int getFuelLimit();
+    int getFuelLimit();
 
     /**
      * Removes some fuel from the turtles fuel supply. Negative numbers can be passed in to INCREASE the fuel level of the turtle.
@@ -179,7 +187,7 @@ public interface ITurtleAccess
      * greater than the current fuel level of the turtle. No fuel will be consumed if {@code false} is returned.
      * @throws UnsupportedOperationException When attempting to consume fuel on the client side.
      */
-    public boolean consumeFuel( int fuel );
+    boolean consumeFuel( int fuel );
 
     /**
      * Increase the turtle's fuel level by the given amount.
@@ -187,7 +195,7 @@ public interface ITurtleAccess
      * @param fuel The amount to refuel with.
      * @throws UnsupportedOperationException When attempting to refuel on the client side.
      */
-    public void addFuel( int fuel );
+    void addFuel( int fuel );
 
     /**
      * Adds a custom command to the turtles command queue. Unlike peripheral methods, these custom commands will be executed
@@ -209,7 +217,8 @@ public interface ITurtleAccess
      * @see ITurtleCommand
      * @see ILuaContext#pullEvent(String)
      */
-    public Object[] executeCommand( ILuaContext context, ITurtleCommand command ) throws LuaException, InterruptedException;
+    @Nonnull
+    Object[] executeCommand( @Nonnull ILuaContext context, @Nonnull ITurtleCommand command ) throws LuaException, InterruptedException;
 
     /**
      * Start playing a specific animation. This will prevent other turtle commands from executing until
@@ -219,7 +228,7 @@ public interface ITurtleAccess
      * @throws UnsupportedOperationException When attempting to execute play an animation on the client side.
      * @see TurtleAnimation
      */
-    public void playAnimation( TurtleAnimation animation );
+    void playAnimation( @Nonnull TurtleAnimation animation );
 
     /**
      * Returns the turtle on the specified side of the turtle, if there is one.
@@ -228,7 +237,8 @@ public interface ITurtleAccess
      * @return The upgrade on the specified side of the turtle, if there is one.
      * @see #setUpgrade(TurtleSide, ITurtleUpgrade)
      */
-    public ITurtleUpgrade getUpgrade( TurtleSide side );
+    @Nullable
+    ITurtleUpgrade getUpgrade( @Nonnull TurtleSide side );
 
     /**
      * Set the upgrade for a given side, resetting peripherals and clearing upgrade specific data.
@@ -237,7 +247,7 @@ public interface ITurtleAccess
      * @param upgrade The upgrade to set, may be {@code null} to clear.
      * @see #getUpgrade(TurtleSide)
      */
-    public void setUpgrade( TurtleSide side, ITurtleUpgrade upgrade );
+    void setUpgrade( @Nonnull TurtleSide side, @Nullable ITurtleUpgrade upgrade );
 
     /**
      * Returns the peripheral created by the upgrade on the specified side of the turtle, if there is one.
@@ -245,7 +255,8 @@ public interface ITurtleAccess
      * @param side The side to get the peripheral from.
      * @return The peripheral created by the upgrade on the specified side of the turtle, {@code null} if none exists.
      */
-    public IPeripheral getPeripheral( TurtleSide side );
+    @Nullable
+    IPeripheral getPeripheral( @Nonnull TurtleSide side );
 
     /**
      * Get an upgrade-specific NBT compound, which can be used to store arbitrary data.
@@ -257,7 +268,8 @@ public interface ITurtleAccess
      * @return The upgrade-specific data.
      * @see #updateUpgradeNBTData(TurtleSide)
      */
-    public NBTTagCompound getUpgradeNBTData( TurtleSide side );
+    @Nonnull
+    NBTTagCompound getUpgradeNBTData( @Nullable TurtleSide side );
 
     /**
      * Mark the upgrade-specific data as dirty on a specific side. This is required for the data to be synced to the
@@ -266,5 +278,5 @@ public interface ITurtleAccess
      * @param side The side to mark dirty.
      * @see #updateUpgradeNBTData(TurtleSide)
      */
-    public void updateUpgradeNBTData( TurtleSide side );
+    void updateUpgradeNBTData( @Nonnull TurtleSide side );
 }

src/main/java/dan200/computercraft/api/turtle/ITurtleCommand.java

@@ -8,6 +8,8 @@ package dan200.computercraft.api.turtle;
 
 import dan200.computercraft.api.lua.ILuaContext;
 
+import javax.annotation.Nonnull;
+
 /**
  * An interface for objects executing custom turtle commands, used with {@link ITurtleAccess#executeCommand(ILuaContext, ITurtleCommand)}.
  *
@@ -28,5 +30,6 @@ public interface ITurtleCommand
      * @see TurtleCommandResult#failure(String)
      * @see TurtleCommandResult
      */
-    public TurtleCommandResult execute( ITurtleAccess turtle );
+    @Nonnull
+    TurtleCommandResult execute( @Nonnull ITurtleAccess turtle );
 }

src/main/java/dan200/computercraft/api/turtle/ITurtleUpgrade.java

@@ -17,6 +17,8 @@ import net.minecraftforge.fml.relauncher.Side;
 import net.minecraftforge.fml.relauncher.SideOnly;
 import org.apache.commons.lang3.tuple.Pair;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import javax.vecmath.Matrix4f;
 
 
@@ -36,7 +38,8 @@ public interface ITurtleUpgrade
      * @return The unique ID for this upgrade.
      * @see ComputerCraftAPI#registerTurtleUpgrade(ITurtleUpgrade)
      */
-    public ResourceLocation getUpgradeID();
+    @Nonnull
+    ResourceLocation getUpgradeID();
 
     /**
      * Gets a numerical identifier representing this type of turtle upgrade,
@@ -47,7 +50,7 @@ public interface ITurtleUpgrade
      * @return The legacy ID, or -1 if is needed.
      * @see ComputerCraftAPI#registerTurtleUpgrade(ITurtleUpgrade)
      */
-    public int getLegacyUpgradeID();
+    int getLegacyUpgradeID();
 
     /**
      * Return an unlocalised string to describe this type of turtle in turtle item names.
@@ -56,7 +59,8 @@ public interface ITurtleUpgrade
      *
      * @return The localisation key for this upgrade's adjective.
      */
-    public String getUnlocalisedAdjective();
+    @Nonnull
+    String getUnlocalisedAdjective();
 
     /**
      * Return whether this turtle adds a tool or a peripheral to the turtle.
@@ -64,7 +68,8 @@ public interface ITurtleUpgrade
      * @return The type of upgrade this is.
      * @see TurtleUpgradeType for the differences between them.
      */
-    public TurtleUpgradeType getType();
+    @Nonnull
+    TurtleUpgradeType getType();
 
     /**
      * Return an item stack representing the type of item that a turtle must be crafted
@@ -73,7 +78,8 @@ public interface ITurtleUpgrade
      *
      * @return The item stack to craft with, or {@code null} if it cannot be crafted.
      */
-    public ItemStack getCraftingItem();
+    @Nullable
+    ItemStack getCraftingItem();
 
     /**
      * Will only be called for peripheral upgrades. Creates a peripheral for a turtle being placed using this upgrade.
@@ -87,7 +93,8 @@ public interface ITurtleUpgrade
      * @return The newly created peripheral. You may return {@code null} if this upgrade is a Tool
      * and this method is not expected to be called.
      */
-    public IPeripheral createPeripheral( ITurtleAccess turtle, TurtleSide side );
+    @Nullable
+    IPeripheral createPeripheral( @Nonnull ITurtleAccess turtle, @Nonnull TurtleSide side );
 
     /**
      * Will only be called for Tool turtle. Called when turtle.dig() or turtle.attack() is called
@@ -104,7 +111,8 @@ public interface ITurtleUpgrade
      * a swinging animation. You may return {@code null} if this turtle is a Peripheral  and this method is not expected
      * to be called.
      */
-    public TurtleCommandResult useTool( ITurtleAccess turtle, TurtleSide side, TurtleVerb verb, EnumFacing direction );
+    @Nonnull
+    TurtleCommandResult useTool( @Nonnull ITurtleAccess turtle, @Nonnull TurtleSide side, @Nonnull TurtleVerb verb, @Nonnull EnumFacing direction );
 
     /**
      * Called to obtain the model to be used when rendering a turtle peripheral.
@@ -119,7 +127,8 @@ public interface ITurtleUpgrade
      * a transformation of {@code null} has the same effect as the identify matrix.
      */
     @SideOnly(Side.CLIENT)
-    public Pair<IBakedModel, Matrix4f> getModel( ITurtleAccess turtle, TurtleSide side );
+    @Nonnull
+    Pair<IBakedModel, Matrix4f> getModel( @Nullable ITurtleAccess turtle, @Nonnull TurtleSide side );
 
     /**
      * Called once per tick for each turtle which has the upgrade equipped.
@@ -127,5 +136,5 @@ public interface ITurtleUpgrade
      * @param turtle Access to the turtle that the upgrade resides on.
      * @param side   Which side of the turtle (left or right) the upgrade resides on.
      */
-    public void update( ITurtleAccess turtle, TurtleSide side );
+    void update( @Nonnull ITurtleAccess turtle, @Nonnull TurtleSide side );
 }

src/main/java/dan200/computercraft/api/turtle/TurtleCommandResult.java

@@ -8,6 +8,9 @@ package dan200.computercraft.api.turtle;
 
 import net.minecraft.util.EnumFacing;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * Used to indicate the result of executing a turtle command.
  *
@@ -24,6 +27,7 @@ public final class TurtleCommandResult
      *
      * @return A successful command result with no values.
      */
+    @Nonnull
     public static TurtleCommandResult success()
     {
         return success( null );
@@ -35,7 +39,8 @@ public final class TurtleCommandResult
      * @param results The results of executing this command.
      * @return A successful command result with the given values.
      */
-    public static TurtleCommandResult success( Object[] results )
+    @Nonnull
+    public static TurtleCommandResult success( @Nullable Object[] results )
     {
         if( results == null || results.length == 0 )
         {
@@ -52,6 +57,7 @@ public final class TurtleCommandResult
      *
      * @return A failed command result with no message.
      */
+    @Nonnull
     public static TurtleCommandResult failure()
     {
         return failure( null );
@@ -63,7 +69,8 @@ public final class TurtleCommandResult
      * @param errorMessage The error message to provide.
      * @return A failed command result with a message.
      */
-    public static TurtleCommandResult failure( String errorMessage )
+    @Nonnull
+    public static TurtleCommandResult failure( @Nullable String errorMessage )
     {
         if( errorMessage == null )
         {
@@ -101,6 +108,7 @@ public final class TurtleCommandResult
      *
      * @return The command's error message, or {@code null} if it was a success.
      */
+    @Nullable
     public String getErrorMessage()
     {
         return m_errorMessage;
@@ -111,6 +119,7 @@ public final class TurtleCommandResult
      *
      * @return The command's result, or {@code null} if it was a failure.
      */
+    @Nullable
     public Object[] getResults()
     {
         return m_results;

src/main/java/dan200/computercraft/client/proxy/CCTurtleProxyClient.java

@@ -38,6 +38,8 @@ import net.minecraftforge.fml.client.registry.ClientRegistry;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import net.minecraftforge.fml.common.gameevent.TickEvent;
 
+import javax.annotation.Nonnull;
+
 public class CCTurtleProxyClient extends CCTurtleProxyCommon
 {
     public CCTurtleProxyClient()
@@ -56,8 +58,9 @@ public class CCTurtleProxyClient extends CCTurtleProxyCommon
         {
             private ModelResourceLocation turtle_dynamic = new ModelResourceLocation( "computercraft:turtle_dynamic", "inventory" );
 
+            @Nonnull
             @Override
-            public ModelResourceLocation getModelLocation( ItemStack stack )
+            public ModelResourceLocation getModelLocation( @Nonnull ItemStack stack )
             {
                 return turtle_dynamic;
             }
@@ -188,7 +191,7 @@ public class CCTurtleProxyClient extends CCTurtleProxyCommon
     private static class TurtleItemColour implements IItemColor
     {
         @Override
-        public int getColorFromItemstack( ItemStack stack, int tintIndex )
+        public int getColorFromItemstack( @Nonnull ItemStack stack, int tintIndex )
         {
             if( tintIndex == 0 )
             {

src/main/java/dan200/computercraft/client/proxy/ComputerCraftProxyClient.java

@@ -55,6 +55,7 @@ import net.minecraftforge.fml.common.gameevent.TickEvent;
 import net.minecraftforge.fml.relauncher.Side;
 import net.minecraftforge.fml.relauncher.SideOnly;
 
+import javax.annotation.Nonnull;
 import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
@@ -88,8 +89,9 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
             private ModelResourceLocation computer = new ModelResourceLocation( "computercraft:CC-Computer", "inventory" );
             private ModelResourceLocation advanced_computer = new ModelResourceLocation( "computercraft:advanced_computer", "inventory" );
 
+            @Nonnull
             @Override
-            public ModelResourceLocation getModelLocation( ItemStack stack )
+            public ModelResourceLocation getModelLocation( @Nonnull ItemStack stack )
             {
                 ItemComputer itemComputer = (ItemComputer) stack.getItem();
                 ComputerFamily family = itemComputer.getFamily( stack.getItemDamage() );
@@ -121,8 +123,9 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
             private ModelResourceLocation advanced_pocket_computer_on = new ModelResourceLocation( "computercraft:advanced_pocket_computer_on", "inventory" );
             private ModelResourceLocation advanced_pocket_computer_blinking = new ModelResourceLocation( "computercraft:advanced_pocket_computer_blinking", "inventory" );
 
+            @Nonnull
             @Override
-            public ModelResourceLocation getModelLocation( ItemStack stack )
+            public ModelResourceLocation getModelLocation( @Nonnull ItemStack stack )
             {
                 ItemPocketComputer itemPocketComputer = (ItemPocketComputer)stack.getItem();
                 switch( itemPocketComputer.getFamily( stack ) )
@@ -180,7 +183,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         mc.getItemColors().registerItemColorHandler( new IItemColor()
         {
             @Override
-            public int getColorFromItemstack( ItemStack stack, int layout )
+            public int getColorFromItemstack( @Nonnull ItemStack stack, int layout )
             {
                 if( layout != 1 ) return 0xFFFFFF;
 
@@ -219,8 +222,9 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         ModelBakery.registerItemVariants( item, new ResourceLocation( "computercraft", name ) );
         Minecraft.getMinecraft().getRenderItem().getItemModelMesher().register( item, new ItemMeshDefinition()
         {
+            @Nonnull
             @Override
-            public ModelResourceLocation getModelLocation( ItemStack stack )
+            public ModelResourceLocation getModelLocation( @Nonnull ItemStack stack )
             {
                 return res;
             }
@@ -519,7 +523,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
 		}
 
 		@Override
-		public int getColorFromItemstack(ItemStack stack, int layer)
+		public int getColorFromItemstack( @Nonnull ItemStack stack, int layer)
 		{
 			return layer == 0 ? 0xFFFFFF : disk.getColor(stack);
 		}

src/main/java/dan200/computercraft/client/render/TileEntityMonitorRenderer.java

@@ -24,6 +24,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.BlockPos;
 import org.lwjgl.opengl.GL11;
 
+import javax.annotation.Nonnull;
+
 public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMonitor>
 {
     public TileEntityMonitorRenderer()
@@ -31,7 +33,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
     }
 
     @Override
-    public void renderTileEntityAt( TileMonitor tileEntity, double posX, double posY, double posZ, float f, int i )
+    public void renderTileEntityAt( @Nonnull TileMonitor tileEntity, double posX, double posY, double posZ, float f, int i )
     {
         if( tileEntity != null )
         {

src/main/java/dan200/computercraft/client/render/TileEntityTurtleRenderer.java

@@ -41,6 +41,7 @@ import net.minecraftforge.client.model.pipeline.LightUtil;
 import org.apache.commons.lang3.tuple.Pair;
 import org.lwjgl.opengl.GL11;
 
+import javax.annotation.Nonnull;
 import javax.vecmath.Matrix4f;
 import java.util.List;
 
@@ -75,7 +76,7 @@ public class TileEntityTurtleRenderer extends TileEntitySpecialRenderer<TileTurt
     }
 
     @Override
-    public void renderTileEntityAt( TileTurtle tileEntity, double posX, double posY, double posZ, float f, int i )
+    public void renderTileEntityAt( @Nonnull TileTurtle tileEntity, double posX, double posY, double posZ, float f, int i )
     {
         if( tileEntity != null )
         {

src/main/java/dan200/computercraft/client/render/TurtleMultiModel.java

@@ -10,6 +10,7 @@ import net.minecraft.client.renderer.vertex.VertexFormat;
 import net.minecraft.client.renderer.vertex.VertexFormatElement;
 import net.minecraft.util.EnumFacing;
 
+import javax.annotation.Nonnull;
 import javax.vecmath.Matrix4f;
 import javax.vecmath.Point3f;
 import java.util.ArrayList;
@@ -39,6 +40,7 @@ public class TurtleMultiModel implements IBakedModel
         m_faceQuads = new List[6];
     }
 
+    @Nonnull
     @Override
     public List<BakedQuad> getQuads( IBlockState state, EnumFacing side, long rand )
     {
@@ -107,18 +109,21 @@ public class TurtleMultiModel implements IBakedModel
         return m_baseModel.isBuiltInRenderer();
     }
 
+    @Nonnull
     @Override
     public TextureAtlasSprite getParticleTexture()
     {
         return m_baseModel.getParticleTexture();
     }
 
+    @Nonnull
     @Override
     public ItemCameraTransforms getItemCameraTransforms()
     {
         return m_baseModel.getItemCameraTransforms();
     }
 
+    @Nonnull
     @Override
     public ItemOverrideList getOverrides()
     {

src/main/java/dan200/computercraft/client/render/TurtleSmartItemModel.java

@@ -30,6 +30,7 @@ import net.minecraftforge.client.model.IModel;
 import net.minecraftforge.client.model.ISmartVariant;
 import org.apache.commons.lang3.tuple.Pair;
 
+import javax.annotation.Nonnull;
 import javax.vecmath.Matrix4f;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -102,8 +103,9 @@ public class TurtleSmartItemModel implements IBakedModel, IResourceManagerReload
         m_cachedModels = new HashMap<TurtleModelCombination, IBakedModel>();
         m_overrides = new ItemOverrideList( new ArrayList<ItemOverride>() )
         {
+            @Nonnull
             @Override
-            public IBakedModel handleItemState(IBakedModel originalModel, ItemStack stack, World world, EntityLivingBase entity)
+            public IBakedModel handleItemState( @Nonnull IBakedModel originalModel, ItemStack stack, @Nonnull World world, @Nonnull EntityLivingBase entity)
             {
                 ItemTurtleBase turtle = (ItemTurtleBase) stack.getItem();
                 ComputerFamily family = turtle.getFamily( stack );
@@ -127,6 +129,7 @@ public class TurtleSmartItemModel implements IBakedModel, IResourceManagerReload
         };
     }
 
+    @Nonnull
     @Override
     public ItemOverrideList getOverrides()
     {
@@ -134,7 +137,7 @@ public class TurtleSmartItemModel implements IBakedModel, IResourceManagerReload
     }
 
     @Override
-    public void onResourceManagerReload( IResourceManager resourceManager )
+    public void onResourceManagerReload( @Nonnull IResourceManager resourceManager )
     {
         m_cachedModels.clear();
     }
@@ -173,6 +176,7 @@ public class TurtleSmartItemModel implements IBakedModel, IResourceManagerReload
 
     // These should not be called:
 
+    @Nonnull
     @Override
     public List<BakedQuad> getQuads( IBlockState state, EnumFacing facing, long rand )
     {
@@ -197,12 +201,14 @@ public class TurtleSmartItemModel implements IBakedModel, IResourceManagerReload
         return getDefaultModel().isBuiltInRenderer();
     }
 
+    @Nonnull
     @Override
     public TextureAtlasSprite getParticleTexture()
     {
         return getDefaultModel().getParticleTexture();
     }
 
+    @Nonnull
     @Override
     public ItemCameraTransforms getItemCameraTransforms()
     {

src/main/java/dan200/computercraft/core/apis/BitAPI.java

@@ -9,6 +9,8 @@ package dan200.computercraft.core.apis;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 
+import javax.annotation.Nonnull;
+
 // Contributed by Nia
 // Based on LuaBit (http://luaforge.net/projects/bit)
  
@@ -68,6 +70,7 @@ public class BitAPI implements ILuaAPI
     {
     }
     
+    @Nonnull
     @Override
     public String[] getMethodNames() {
         return new String[] {
@@ -77,7 +80,7 @@ public class BitAPI implements ILuaAPI
     }
     
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         Object a = args.length>0?args[0]:null;
         Object b = args.length>1?args[1]:null;

src/main/java/dan200/computercraft/core/apis/BufferAPI.java

@@ -11,6 +11,8 @@ import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.terminal.TextBuffer;
 
+import javax.annotation.Nonnull;
+
 public class BufferAPI implements ILuaAPI
 {
     private static class BufferLuaObject implements ILuaObject
@@ -22,6 +24,7 @@ public class BufferAPI implements ILuaAPI
             m_buffer = buffer;
         }
 
+        @Nonnull
         @Override
         public String[] getMethodNames()
         {
@@ -35,7 +38,7 @@ public class BufferAPI implements ILuaAPI
         }
 
         @Override
-        public Object[] callMethod( ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException
+        public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
         {
             switch( method )
             {
@@ -165,6 +168,7 @@ public class BufferAPI implements ILuaAPI
     {
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -174,7 +178,7 @@ public class BufferAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -14,6 +14,7 @@ import dan200.computercraft.core.filesystem.FileSystemException;
 import dan200.computercraft.core.filesystem.IMountedFileBinary;
 import dan200.computercraft.core.filesystem.IMountedFileNormal;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
@@ -54,6 +55,7 @@ public class FSAPI implements ILuaAPI
         m_fileSystem = null;
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -78,7 +80,7 @@ public class FSAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -370,6 +372,7 @@ public class FSAPI implements ILuaAPI
     private static Object[] wrapBufferedReader( final IMountedFileNormal reader )
     {
         return new Object[] { new ILuaObject() {
+            @Nonnull
             @Override
             public String[] getMethodNames()
             {
@@ -381,7 +384,7 @@ public class FSAPI implements ILuaAPI
             }
             
             @Override
-            public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
             {
                 switch( method )
                 {
@@ -439,6 +442,7 @@ public class FSAPI implements ILuaAPI
     private static Object[] wrapBufferedWriter( final IMountedFileNormal writer )
     {
         return new Object[] { new ILuaObject() {
+            @Nonnull
             @Override
             public String[] getMethodNames()
             {
@@ -451,7 +455,7 @@ public class FSAPI implements ILuaAPI
             }
             
             @Override
-            public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
             {
                 switch( method )
                 {
@@ -521,6 +525,7 @@ public class FSAPI implements ILuaAPI
         
         return new Object[] { new ILuaObject() {
 
+            @Nonnull
             @Override
             public String[] getMethodNames() {
                 return new String[] {
@@ -530,7 +535,7 @@ public class FSAPI implements ILuaAPI
             }
 
             @Override
-            public Object[] callMethod( ILuaContext context, int method, Object[] args) throws LuaException {
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args) throws LuaException {
                 switch( method )
                 {
                     case 0:
@@ -572,6 +577,7 @@ public class FSAPI implements ILuaAPI
         
         return new Object[] { new ILuaObject() {
 
+            @Nonnull
             @Override
             public String[] getMethodNames() {
                 return new String[] {
@@ -582,7 +588,7 @@ public class FSAPI implements ILuaAPI
             }
 
             @Override
-            public Object[] callMethod( ILuaContext context, int method, Object[] args) throws LuaException {
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args) throws LuaException {
                 switch( method )
                 {
                     case 0:

src/main/java/dan200/computercraft/core/apis/HTTPAPI.java

@@ -10,6 +10,7 @@ import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
 
+import javax.annotation.Nonnull;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.util.*;
@@ -72,6 +73,7 @@ public class HTTPAPI implements ILuaAPI
     private static ILuaObject wrapBufferedReader( final BufferedReader reader, final int responseCode, final Map<String, String> responseHeaders )
     {
         return new ILuaObject() {
+            @Nonnull
             @Override
             public String[] getMethodNames()
             {
@@ -85,7 +87,7 @@ public class HTTPAPI implements ILuaAPI
             }
             
             @Override
-            public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
             {
                 switch( method )
                 {
@@ -164,6 +166,7 @@ public class HTTPAPI implements ILuaAPI
         }
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -174,7 +177,7 @@ public class HTTPAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/core/apis/OSAPI.java

@@ -10,6 +10,7 @@ import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.shared.util.StringUtil;
 
+import javax.annotation.Nonnull;
 import java.util.*;
 
 public class OSAPI implements ILuaAPI
@@ -47,7 +48,7 @@ public class OSAPI implements ILuaAPI
         }
 
         @Override
-        public int compareTo( Alarm o )
+        public int compareTo( @Nonnull Alarm o )
         {
             double t = (double)m_day * 24.0 + m_time;
             double ot = (double)m_day * 24.0 + m_time;
@@ -166,6 +167,7 @@ public class OSAPI implements ILuaAPI
         }
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -216,7 +218,7 @@ public class OSAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/core/apis/PeripheralAPI.java

@@ -18,6 +18,7 @@ import dan200.computercraft.core.computer.ITask;
 import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.filesystem.FileSystemException;
 
+import javax.annotation.Nonnull;
 import java.util.*;
 
 public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChangeListener
@@ -118,13 +119,13 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
         // IComputerAccess implementation
 
         @Override
-        public String mount( String desiredLoc, IMount mount )
+        public String mount( @Nonnull String desiredLoc, @Nonnull IMount mount )
         {
             return mount( desiredLoc, mount, m_side );
         }
 
         @Override
-        public synchronized String mount( String desiredLoc, IMount mount, String driveName )
+        public synchronized String mount( @Nonnull String desiredLoc, @Nonnull IMount mount, @Nonnull String driveName )
         {
             if( !m_attached )
             {
@@ -153,13 +154,13 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
         }
 
         @Override
-        public String mountWritable( String desiredLoc, IWritableMount mount )
+        public String mountWritable( @Nonnull String desiredLoc, @Nonnull IWritableMount mount )
         {
             return mountWritable( desiredLoc, mount, m_side );
         }
 
         @Override
-        public synchronized String mountWritable( String desiredLoc, IWritableMount mount, String driveName )
+        public synchronized String mountWritable( @Nonnull String desiredLoc, @Nonnull IWritableMount mount, @Nonnull String driveName )
         {
             if( !m_attached )
             {
@@ -215,7 +216,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
         }
                 
         @Override
-        public synchronized void queueEvent( final String event, final Object[] arguments )
+        public synchronized void queueEvent( @Nonnull final String event, final Object[] arguments )
         {
             if( !m_attached ) {
                 throw new RuntimeException( "You are not attached to this Computer" );
@@ -223,6 +224,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             m_environment.queueEvent( event, arguments );
         }
         
+        @Nonnull
         @Override
         public synchronized String getAttachmentName()
         {
@@ -372,6 +374,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
         }
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -384,7 +387,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/core/apis/RedstoneAPI.java

@@ -10,6 +10,7 @@ import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.computer.Computer;
 
+import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -45,6 +46,7 @@ public class RedstoneAPI implements ILuaAPI
     {
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -67,7 +69,7 @@ public class RedstoneAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/core/apis/TermAPI.java

@@ -11,6 +11,8 @@ import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.computer.IComputerEnvironment;
 import dan200.computercraft.core.terminal.Terminal;
 
+import javax.annotation.Nonnull;
+
 public class TermAPI implements ILuaAPI
 {
     private Terminal m_terminal;
@@ -45,6 +47,7 @@ public class TermAPI implements ILuaAPI
     {
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -102,7 +105,7 @@ public class TermAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/core/filesystem/ComboMount.java

@@ -8,6 +8,7 @@ package dan200.computercraft.core.filesystem;
 
 import dan200.computercraft.api.filesystem.IMount;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
@@ -27,7 +28,7 @@ public class ComboMount implements IMount
     // IMount implementation
     
     @Override
-    public boolean exists( String path ) throws IOException
+    public boolean exists( @Nonnull String path ) throws IOException
     {
         for( int i=m_parts.length-1; i>=0; --i )
         {
@@ -41,7 +42,7 @@ public class ComboMount implements IMount
     }
     
     @Override
-    public boolean isDirectory( String path ) throws IOException
+    public boolean isDirectory( @Nonnull String path ) throws IOException
     {
         for( int i=m_parts.length-1; i>=0; --i )
         {
@@ -55,7 +56,7 @@ public class ComboMount implements IMount
     }
     
     @Override
-    public void list( String path, List<String> contents ) throws IOException
+    public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
     {
         // Combine the lists from all the mounts
         List<String> foundFiles = null;
@@ -99,7 +100,7 @@ public class ComboMount implements IMount
     }
     
     @Override
-    public long getSize( String path ) throws IOException
+    public long getSize( @Nonnull String path ) throws IOException
     {
         for( int i=m_parts.length-1; i>=0; --i )
         {
@@ -112,8 +113,9 @@ public class ComboMount implements IMount
         throw new IOException( "No such file" );
     }
 
+    @Nonnull
     @Override
-    public InputStream openForRead( String path ) throws IOException
+    public InputStream openForRead( @Nonnull String path ) throws IOException
     {
         for( int i=m_parts.length-1; i>=0; --i )
         {

src/main/java/dan200/computercraft/core/filesystem/EmptyMount.java

@@ -8,6 +8,7 @@ package dan200.computercraft.core.filesystem;
 
 import dan200.computercraft.api.filesystem.IMount;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
@@ -21,30 +22,31 @@ public class EmptyMount implements IMount
     // IMount implementation
     
     @Override
-    public boolean exists( String path ) throws IOException
+    public boolean exists( @Nonnull String path ) throws IOException
     {
         return path.isEmpty();
     }
     
     @Override
-    public boolean isDirectory( String path ) throws IOException
+    public boolean isDirectory( @Nonnull String path ) throws IOException
     {
         return path.isEmpty();
     }
     
     @Override
-    public void list( String path, List<String> contents ) throws IOException
+    public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
     {
     }
     
     @Override
-    public long getSize( String path ) throws IOException
+    public long getSize( @Nonnull String path ) throws IOException
     {
         return 0;
     }
 
+    @Nonnull
     @Override
-    public InputStream openForRead( String path ) throws IOException
+    public InputStream openForRead( @Nonnull String path ) throws IOException
     {
         return null;
     }

src/main/java/dan200/computercraft/core/filesystem/FileMount.java

@@ -8,6 +8,7 @@ package dan200.computercraft.core.filesystem;
 
 import dan200.computercraft.api.filesystem.IWritableMount;
 
+import javax.annotation.Nonnull;
 import java.io.*;
 import java.util.List;
 
@@ -39,14 +40,14 @@ public class FileMount implements IWritableMount
         }
         
         @Override
-        public void write( byte[] b ) throws IOException
+        public void write( @Nonnull byte[] b ) throws IOException
         {
             count( b.length );
             m_innerStream.write( b );
         }
         
         @Override
-        public void write( byte[] b, int off, int len ) throws IOException 
+        public void write( @Nonnull byte[] b, int off, int len ) throws IOException
         {
             count( len );
             m_innerStream.write( b, off, len );
@@ -94,7 +95,7 @@ public class FileMount implements IWritableMount
     // IMount implementation
     
     @Override
-    public boolean exists( String path ) throws IOException
+    public boolean exists( @Nonnull String path ) throws IOException
     {
         if( !created() )
         {
@@ -108,7 +109,7 @@ public class FileMount implements IWritableMount
     }
     
     @Override
-    public boolean isDirectory( String path ) throws IOException
+    public boolean isDirectory( @Nonnull String path ) throws IOException
     {
         if( !created() )
         {
@@ -122,7 +123,7 @@ public class FileMount implements IWritableMount
     }
     
     @Override
-    public void list( String path, List<String> contents ) throws IOException
+    public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
     {
         if( !created() )
         {
@@ -153,7 +154,7 @@ public class FileMount implements IWritableMount
     }
 
     @Override
-    public long getSize( String path ) throws IOException
+    public long getSize( @Nonnull String path ) throws IOException
     {
         if( !created() )
         {
@@ -180,8 +181,9 @@ public class FileMount implements IWritableMount
         throw new IOException( "No such file" );
     }
     
+    @Nonnull
     @Override
-    public InputStream openForRead( String path ) throws IOException
+    public InputStream openForRead( @Nonnull String path ) throws IOException
     {
         if( created() )
         {
@@ -197,7 +199,7 @@ public class FileMount implements IWritableMount
     // IWritableMount implementation
     
     @Override
-    public void makeDirectory( String path ) throws IOException
+    public void makeDirectory( @Nonnull String path ) throws IOException
     {
         create();
         File file = getRealPath( path );
@@ -236,7 +238,7 @@ public class FileMount implements IWritableMount
     }
     
     @Override
-    public void delete( String path ) throws IOException
+    public void delete( @Nonnull String path ) throws IOException
     {
         if( path.length() == 0 )
         {
@@ -278,8 +280,9 @@ public class FileMount implements IWritableMount
         }
     }
     
+    @Nonnull
     @Override
-    public OutputStream openForWrite( String path ) throws IOException
+    public OutputStream openForWrite( @Nonnull String path ) throws IOException
     {
         create();
         File file = getRealPath( path );
@@ -309,8 +312,9 @@ public class FileMount implements IWritableMount
         }
     }
     
+    @Nonnull
     @Override
-    public OutputStream openForAppend( String path ) throws IOException
+    public OutputStream openForAppend( @Nonnull String path ) throws IOException
     {
         if( created() )
         {

src/main/java/dan200/computercraft/core/filesystem/JarMount.java

@@ -8,6 +8,7 @@ package dan200.computercraft.core.filesystem;
 
 import dan200.computercraft.api.filesystem.IMount;
 
+import javax.annotation.Nonnull;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -178,14 +179,14 @@ public class JarMount implements IMount
     // IMount implementation
     
     @Override
-    public boolean exists( String path ) throws IOException
+    public boolean exists( @Nonnull String path ) throws IOException
     {
         FileInZip file = m_root.getFile( path );
         return file != null;
     }
     
     @Override
-    public boolean isDirectory( String path ) throws IOException
+    public boolean isDirectory( @Nonnull String path ) throws IOException
     {
         FileInZip file = m_root.getFile( path );
         if( file != null )
@@ -196,7 +197,7 @@ public class JarMount implements IMount
     }
     
     @Override
-    public void list( String path, List<String> contents ) throws IOException
+    public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
     {
         FileInZip file = m_root.getFile( path );
         if( file != null && file.isDirectory() )
@@ -210,7 +211,7 @@ public class JarMount implements IMount
     }
     
     @Override
-    public long getSize( String path ) throws IOException
+    public long getSize( @Nonnull String path ) throws IOException
     {
         FileInZip file = m_root.getFile( path );
         if( file != null )
@@ -220,8 +221,9 @@ public class JarMount implements IMount
         throw new IOException( "No such file" );
     }
 
+    @Nonnull
     @Override
-    public InputStream openForRead( String path ) throws IOException
+    public InputStream openForRead( @Nonnull String path ) throws IOException
     {
         FileInZip file = m_root.getFile( path );
         if( file != null && !file.isDirectory() )

src/main/java/dan200/computercraft/core/filesystem/SubMount.java

@@ -8,6 +8,7 @@ package dan200.computercraft.core.filesystem;
 
 import dan200.computercraft.api.filesystem.IMount;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
@@ -26,31 +27,32 @@ public class SubMount implements IMount
     // IMount implementation
     
     @Override
-    public boolean exists( String path ) throws IOException
+    public boolean exists( @Nonnull String path ) throws IOException
     {
         return m_parent.exists( getFullPath( path ) );
     }
     
     @Override
-    public boolean isDirectory( String path ) throws IOException
+    public boolean isDirectory( @Nonnull String path ) throws IOException
     {
         return m_parent.isDirectory( getFullPath( path ) );
     }
     
     @Override
-    public void list( String path, List<String> contents ) throws IOException
+    public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
     {
         m_parent.list( getFullPath( path ), contents );
     }
     
     @Override
-    public long getSize( String path ) throws IOException
+    public long getSize( @Nonnull String path ) throws IOException
     {
         return m_parent.getSize( getFullPath( path ) );
     }
 
+    @Nonnull
     @Override
-    public InputStream openForRead( String path ) throws IOException
+    public InputStream openForRead( @Nonnull String path ) throws IOException
     {
         return m_parent.openForRead( getFullPath( path ) );
     }

src/main/java/dan200/computercraft/core/lua/LuaJLuaMachine.java

@@ -21,6 +21,7 @@ import org.luaj.vm2.lib.VarArgFunction;
 import org.luaj.vm2.lib.ZeroArgFunction;
 import org.luaj.vm2.lib.jse.JsePlatform;
 
+import javax.annotation.Nonnull;
 import java.io.*;
 import java.util.HashMap;
 import java.util.IdentityHashMap;
@@ -339,6 +340,7 @@ public class LuaJLuaMachine implements ILuaMachine
                         try
                         {
                             results = apiObject.callMethod( new ILuaContext() {
+                                @Nonnull
                                 @Override
                                 public Object[] pullEvent( String filter ) throws LuaException, InterruptedException
                                 {
@@ -350,12 +352,14 @@ public class LuaJLuaMachine implements ILuaMachine
                                     return results;
                                 }
                                 
+                                @Nonnull
                                 @Override
                                 public Object[] pullEventRaw( String filter ) throws InterruptedException
                                 {
                                     return yield( new Object[] { filter } );
                                 }
                                 
+                                @Nonnull
                                 @Override
                                 public Object[] yield( Object[] yieldArgs ) throws InterruptedException
                                 {
@@ -372,7 +376,7 @@ public class LuaJLuaMachine implements ILuaMachine
                                 }
 
                                 @Override
-                                public long issueMainThreadTask( final ILuaTask task ) throws LuaException
+                                public long issueMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException
                                 {
                                     // Issue command
                                     final long taskID = MainThread.getUniqueTaskID();
@@ -431,7 +435,7 @@ public class LuaJLuaMachine implements ILuaMachine
                                 }
 
                                 @Override
-                                public Object[] executeMainThreadTask( final ILuaTask task ) throws LuaException, InterruptedException
+                                public Object[] executeMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException, InterruptedException
                                 {
                                     // Issue task
                                     final long taskID = issueMainThreadTask( task );

src/main/java/dan200/computercraft/shared/common/BlockGeneric.java

@@ -25,6 +25,7 @@ import net.minecraft.world.Explosion;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
@@ -43,12 +44,13 @@ public abstract class BlockGeneric extends Block implements
     protected abstract TileGeneric createTile( int damage );
 
     @Override
-    public final void dropBlockAsItemWithChance( World world, BlockPos pos, IBlockState state, float chance, int fortune )
+    public final void dropBlockAsItemWithChance( World world, @Nonnull BlockPos pos, @Nonnull IBlockState state, float chance, int fortune )
     {
     }
 
+    @Nonnull
     @Override
-    public final List<ItemStack> getDrops( IBlockAccess world, BlockPos pos, IBlockState state, int fortune )
+    public final List<ItemStack> getDrops( IBlockAccess world, BlockPos pos, @Nonnull IBlockState state, int fortune )
     {
         ArrayList<ItemStack> drops = new ArrayList<ItemStack>( 1 );
         TileEntity tile = world.getTileEntity( pos );
@@ -60,6 +62,7 @@ public abstract class BlockGeneric extends Block implements
         return drops;
     }
 
+    @Nonnull
     @Override
     public final IBlockState onBlockPlaced( World world, BlockPos pos, EnumFacing side, float hitX, float hitY, float hitZ, int damage, EntityLivingBase placer )
     {
@@ -67,7 +70,7 @@ public abstract class BlockGeneric extends Block implements
     }
 
     @Override
-    public final boolean removedByPlayer( IBlockState state, World world, BlockPos pos, EntityPlayer player, boolean willHarvest )
+    public final boolean removedByPlayer( @Nonnull IBlockState state, World world, @Nonnull BlockPos pos, @Nonnull EntityPlayer player, boolean willHarvest )
     {
         if( !world.isRemote )
         {
@@ -109,7 +112,7 @@ public abstract class BlockGeneric extends Block implements
     }
 
     @Override
-    public final void breakBlock( World world, BlockPos pos, IBlockState newState )
+    public final void breakBlock( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull IBlockState newState )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileGeneric )
@@ -121,8 +124,9 @@ public abstract class BlockGeneric extends Block implements
         world.removeTileEntity( pos );
     }
 
+    @Nonnull
     @Override
-    public final ItemStack getPickBlock( IBlockState state, RayTraceResult target, World world, BlockPos pos, EntityPlayer player )
+    public final ItemStack getPickBlock( @Nonnull IBlockState state, RayTraceResult target, @Nonnull World world, @Nonnull BlockPos pos, EntityPlayer player )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileGeneric )
@@ -134,7 +138,7 @@ public abstract class BlockGeneric extends Block implements
     }
 
     @Override
-    protected final ItemStack createStackedBlock( IBlockState state )
+    protected final ItemStack createStackedBlock( @Nonnull IBlockState state )
     {
         return null;
     }
@@ -174,7 +178,7 @@ public abstract class BlockGeneric extends Block implements
     }
 
     @Override
-    public final boolean isSideSolid( IBlockState state, IBlockAccess world, BlockPos pos, EnumFacing side )
+    public final boolean isSideSolid( IBlockState state, @Nonnull IBlockAccess world, @Nonnull BlockPos pos, EnumFacing side )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileGeneric )
@@ -192,7 +196,7 @@ public abstract class BlockGeneric extends Block implements
     }
 
     @Override
-    public float getExplosionResistance( World world, BlockPos pos, Entity exploder, Explosion explosion )
+    public float getExplosionResistance( World world, BlockPos pos, @Nonnull Entity exploder, Explosion explosion )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileGeneric && tile.hasWorldObj() )
@@ -206,6 +210,7 @@ public abstract class BlockGeneric extends Block implements
         return super.getExplosionResistance( exploder );
     }
 
+    @Nonnull
     @Override
     public final AxisAlignedBB getBoundingBox( IBlockState state, IBlockAccess world, BlockPos pos )
     {
@@ -218,14 +223,15 @@ public abstract class BlockGeneric extends Block implements
         return FULL_BLOCK_AABB;
     }
 
+    @Nonnull
     @Override
-    public AxisAlignedBB getSelectedBoundingBox( IBlockState state, World worldIn, BlockPos pos )
+    public final AxisAlignedBB getSelectedBoundingBox( IBlockState state, @Nonnull World world, @Nonnull BlockPos pos )
     {
-        return getBoundingBox( state, worldIn, pos ).offset( pos );
+        return getBoundingBox( state, world, pos ).offset( pos );
     }
 
     @Override
-    public final AxisAlignedBB getCollisionBoundingBox( IBlockState state, World world, BlockPos pos )
+    public final AxisAlignedBB getCollisionBoundingBox( IBlockState state, @Nonnull World world, @Nonnull BlockPos pos )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileGeneric && tile.hasWorldObj() )
@@ -252,7 +258,7 @@ public abstract class BlockGeneric extends Block implements
     }
 
     @Override
-    public final void addCollisionBoxToList( IBlockState state, World world, BlockPos pos, AxisAlignedBB bigBox, List<AxisAlignedBB> list, Entity entity )
+    public final void addCollisionBoxToList( IBlockState state, @Nonnull World world, @Nonnull BlockPos pos, @Nonnull AxisAlignedBB bigBox, @Nonnull List<AxisAlignedBB> list, Entity entity )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileGeneric && tile.hasWorldObj() )
@@ -349,14 +355,16 @@ public abstract class BlockGeneric extends Block implements
         return true;
     }
 
+    @Nonnull
     @Override
-    public final TileEntity createTileEntity( World world, IBlockState state )
+    public final TileEntity createTileEntity( @Nonnull World world, @Nonnull IBlockState state )
     {
         return createTile( state );
     }
 
+    @Nonnull
     @Override
-    public final TileEntity createNewTileEntity( World world, int damage )
+    public final TileEntity createNewTileEntity( @Nonnull World world, int damage )
     {
         return createTile( damage );
     }

src/main/java/dan200/computercraft/shared/common/DefaultBundledRedstoneProvider.java

@@ -12,6 +12,8 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class DefaultBundledRedstoneProvider implements IBundledRedstoneProvider
 {
     public DefaultBundledRedstoneProvider()
@@ -19,7 +21,7 @@ public class DefaultBundledRedstoneProvider implements IBundledRedstoneProvider
     }
 
     @Override
-    public int getBundledRedstoneOutput( World world, BlockPos pos, EnumFacing side )
+    public int getBundledRedstoneOutput( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side )
     {
         return getDefaultBundledRedstoneOutput( world, pos, side );
     }

src/main/java/dan200/computercraft/shared/common/TileGeneric.java

@@ -23,6 +23,8 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.List;
 
 public abstract class TileGeneric extends TileEntity
@@ -48,6 +50,7 @@ public abstract class TileGeneric extends TileEntity
     {
     }
 
+    @Nullable
     public BlockGeneric getBlock()
     {
         Block block = worldObj.getBlockState( getPos() ).getBlock();
@@ -77,7 +80,7 @@ public abstract class TileGeneric extends TileEntity
         worldObj.setBlockState( getPos(), newState, 3 );
     }
 
-    public void getDroppedItems( List<ItemStack> drops, boolean creative )
+    public void getDroppedItems( @Nonnull List<ItemStack> drops, boolean creative )
     {
     }
 
@@ -95,7 +98,7 @@ public abstract class TileGeneric extends TileEntity
     {
     }
 
-    public void onNeighbourTileEntityChange( BlockPos neighbour )
+    public void onNeighbourTileEntityChange( @Nonnull BlockPos neighbour )
     {
     }
 
@@ -109,12 +112,13 @@ public abstract class TileGeneric extends TileEntity
         return false;
     }
 
+    @Nonnull
     public AxisAlignedBB getBounds()
     {
         return new AxisAlignedBB( 0.0, 0.0, 0.0, 1.0, 1.0, 1.0 );
     }
 
-    public void getCollisionBounds( List<AxisAlignedBB> bounds )
+    public void getCollisionBounds( @Nonnull List<AxisAlignedBB> bounds )
     {
         bounds.add( getBounds() );
     }
@@ -129,12 +133,12 @@ public abstract class TileGeneric extends TileEntity
         return 0;
     }
 
-    public boolean getBundledRedstoneConnectivity( EnumFacing side )
+    public boolean getBundledRedstoneConnectivity( @Nonnull EnumFacing side )
     {
         return false;
     }
 
-    public int getBundledRedstoneOutput( EnumFacing side )
+    public int getBundledRedstoneOutput( @Nonnull EnumFacing side )
     {
         return 0;
     }
@@ -163,11 +167,11 @@ public abstract class TileGeneric extends TileEntity
         return false;
     }
 
-    protected void writeDescription( NBTTagCompound nbttagcompound )
+    protected void writeDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
     }
 
-    protected void readDescription( NBTTagCompound nbttagcompound )
+    protected void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
     }
 
@@ -186,7 +190,7 @@ public abstract class TileGeneric extends TileEntity
     }
 
     @Override
-    public boolean shouldRefresh( World world, BlockPos pos, IBlockState oldState, IBlockState newState )
+    public boolean shouldRefresh( World world, BlockPos pos, @Nonnull IBlockState oldState, @Nonnull IBlockState newState )
     {
         return newState.getBlock() != oldState.getBlock();
     }
@@ -215,6 +219,7 @@ public abstract class TileGeneric extends TileEntity
         }
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound getUpdateTag ()
     {
@@ -224,7 +229,7 @@ public abstract class TileGeneric extends TileEntity
     }
 
     @Override
-    public void handleUpdateTag (NBTTagCompound tag)
+    public void handleUpdateTag ( @Nonnull NBTTagCompound tag)
     {
         super.handleUpdateTag(tag);
         readDescription( tag );

src/main/java/dan200/computercraft/shared/computer/apis/CommandAPI.java

@@ -24,6 +24,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.ResourceLocation;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -61,6 +62,7 @@ public class CommandAPI implements ILuaAPI
     {
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -139,7 +141,7 @@ public class CommandAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/shared/computer/blocks/BlockCommandComputer.java

@@ -25,6 +25,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class BlockCommandComputer extends BlockComputerBase
 {
     // Statics
@@ -50,6 +52,7 @@ public class BlockCommandComputer extends BlockComputerBase
         );
     }
 
+    @Nonnull
     @Override
     protected BlockStateContainer createBlockState()
     {
@@ -59,6 +62,7 @@ public class BlockCommandComputer extends BlockComputerBase
         });
     }
 
+    @Nonnull
     @Override
     public IBlockState getStateFromMeta( int meta )
     {
@@ -76,8 +80,9 @@ public class BlockCommandComputer extends BlockComputerBase
         return ((EnumFacing)state.getValue( Properties.FACING )).getIndex();
     }
 
+    @Nonnull
     @Override
-    public IBlockState getActualState( IBlockState state, IBlockAccess world, BlockPos pos )
+    public IBlockState getActualState( @Nonnull IBlockState state, IBlockAccess world, BlockPos pos )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof IComputerTile )

src/main/java/dan200/computercraft/shared/computer/blocks/BlockComputer.java

@@ -27,6 +27,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class BlockComputer extends BlockComputerBase
 {
     // Statics
@@ -52,6 +54,7 @@ public class BlockComputer extends BlockComputerBase
         );
     }
 
+    @Nonnull
     @Override
     protected BlockStateContainer createBlockState()
     {
@@ -62,6 +65,7 @@ public class BlockComputer extends BlockComputerBase
         });
     }
 
+    @Nonnull
     @Override
     public IBlockState getStateFromMeta( int meta )
     {
@@ -117,8 +121,9 @@ public class BlockComputer extends BlockComputerBase
         }
     }
 
+    @Nonnull
     @Override
-    public IBlockState getActualState( IBlockState state, IBlockAccess world, BlockPos pos )
+    public IBlockState getActualState( @Nonnull IBlockState state, IBlockAccess world, BlockPos pos )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof IComputerTile )

src/main/java/dan200/computercraft/shared/computer/blocks/ComputerPeripheral.java

@@ -12,6 +12,8 @@ import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 
+import javax.annotation.Nonnull;
+
 public class ComputerPeripheral
     implements IPeripheral
 {
@@ -26,12 +28,14 @@ public class ComputerPeripheral
         
     // IPeripheral implementation
 
+    @Nonnull
     @Override
     public String getType()
     {
         return m_type;
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -45,7 +49,7 @@ public class ComputerPeripheral
     }
 
     @Override
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object[] arguments ) throws LuaException
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -87,12 +91,12 @@ public class ComputerPeripheral
     }
 
     @Override
-    public void attach( IComputerAccess computer )
+    public void attach( @Nonnull IComputerAccess computer )
     {
     }
 
     @Override
-    public void detach( IComputerAccess computer )
+    public void detach( @Nonnull IComputerAccess computer )
     {
     }
 

src/main/java/dan200/computercraft/shared/computer/blocks/ComputerState.java

@@ -8,6 +8,8 @@ package dan200.computercraft.shared.computer.blocks;
 
 import net.minecraft.util.IStringSerializable;
 
+import javax.annotation.Nonnull;
+
 public enum ComputerState implements IStringSerializable
 {
     Off( "off" ),
@@ -21,6 +23,7 @@ public enum ComputerState implements IStringSerializable
         m_name = name;
     }
 
+    @Nonnull
     @Override
     public String getName()
     {

src/main/java/dan200/computercraft/shared/computer/blocks/TileCommandComputer.java

@@ -21,6 +21,7 @@ import net.minecraft.util.text.*;
 import net.minecraft.util.*;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.HashMap;
 import java.util.Map;
@@ -53,6 +54,7 @@ public class TileCommandComputer extends TileComputer
 
         // ICommandSender
 
+        @Nonnull
         @Override
         public ITextComponent getDisplayName()
         {
@@ -69,7 +71,7 @@ public class TileCommandComputer extends TileComputer
         }
 
         @Override
-        public void addChatMessage( ITextComponent chatComponent )
+        public void addChatMessage( @Nonnull ITextComponent chatComponent )
         {
             m_outputTable.put( m_outputTable.size() + 1, chatComponent.getUnformattedText() );
         }
@@ -80,12 +82,14 @@ public class TileCommandComputer extends TileComputer
             return level <= 2;
         }
 
+        @Nonnull
         @Override
         public BlockPos getPosition()
         {
             return TileCommandComputer.this.getPos();
         }
 
+        @Nonnull
         @Override
         public Vec3d getPositionVector()
         {
@@ -93,6 +97,7 @@ public class TileCommandComputer extends TileComputer
             return new Vec3d( pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5 );
         }
 
+        @Nonnull
         @Override
         public World getEntityWorld()
         {
@@ -126,7 +131,7 @@ public class TileCommandComputer extends TileComputer
         }
 
         @Override
-        public void fillInInfo( ByteBuf buf )
+        public void fillInInfo( @Nonnull ByteBuf buf )
         {
         }
     }

src/main/java/dan200/computercraft/shared/computer/blocks/TileComputer.java

@@ -17,6 +17,7 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.EnumFacing;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class TileComputer extends TileComputerBase
@@ -47,7 +48,7 @@ public class TileComputer extends TileComputerBase
     }
 
     @Override
-    public void getDroppedItems( List<ItemStack> drops, boolean creative )
+    public void getDroppedItems( @Nonnull List<ItemStack> drops, boolean creative )
     {
         IComputer computer = getComputer();
         if( !creative || (computer != null && computer.getLabel() != null) )
@@ -69,7 +70,7 @@ public class TileComputer extends TileComputerBase
     }
 
     @Override
-    public final void readDescription( NBTTagCompound nbttagcompound )
+    public final void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         updateBlock();

src/main/java/dan200/computercraft/shared/computer/blocks/TileComputerBase.java

@@ -27,6 +27,8 @@ import net.minecraft.util.EnumHand;
 import net.minecraft.util.ITickable;
 import net.minecraft.util.math.BlockPos;
 
+import javax.annotation.Nonnull;
+
 public abstract class TileComputerBase extends TileGeneric
     implements IComputerTile, IDirectionalTile, ITickable
 {
@@ -167,14 +169,14 @@ public abstract class TileComputerBase extends TileGeneric
     }
 
     @Override
-    public boolean getBundledRedstoneConnectivity( EnumFacing side )
+    public boolean getBundledRedstoneConnectivity( @Nonnull EnumFacing side )
     {
         int localDir = remapLocalSide( DirectionUtil.toLocal( this, side ) );
         return !isRedstoneBlockedOnSide( localDir );
     }
 
     @Override
-    public int getBundledRedstoneOutput( EnumFacing side )
+    public int getBundledRedstoneOutput( @Nonnull EnumFacing side )
     {
         int localDir = remapLocalSide( DirectionUtil.toLocal( this, side ) );
         if( !isRedstoneBlockedOnSide( localDir ) )
@@ -198,7 +200,7 @@ public abstract class TileComputerBase extends TileGeneric
     }
 
     @Override
-    public void onNeighbourTileEntityChange( BlockPos neighbour )
+    public void onNeighbourTileEntityChange( @Nonnull BlockPos neighbour )
     {
         updateInput( neighbour );
     }
@@ -239,6 +241,7 @@ public abstract class TileComputerBase extends TileGeneric
         }
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT( NBTTagCompound nbttagcompound )
     {
@@ -517,14 +520,14 @@ public abstract class TileComputerBase extends TileGeneric
     // Networking stuff
 
     @Override
-    public void writeDescription( NBTTagCompound nbttagcompound )
+    public void writeDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.writeDescription( nbttagcompound );
         nbttagcompound.setInteger( "instanceID", createServerComputer().getInstanceID() );
     }
 
     @Override
-    public void readDescription( NBTTagCompound nbttagcompound )
+    public void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         m_instanceID = nbttagcompound.getInteger( "instanceID" );

src/main/java/dan200/computercraft/shared/computer/inventory/ContainerComputer.java

@@ -12,6 +12,7 @@ import dan200.computercraft.shared.computer.core.IContainerComputer;
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.inventory.Container;
 
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 public class ContainerComputer extends Container
@@ -25,7 +26,7 @@ public class ContainerComputer extends Container
     }
     
     @Override
-    public boolean canInteractWith( EntityPlayer player )
+    public boolean canInteractWith( @Nonnull EntityPlayer player )
     {
         return m_computer.isUseableByPlayer( player );
     }

src/main/java/dan200/computercraft/shared/computer/items/ItemCommandComputer.java

@@ -14,6 +14,7 @@ import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemCommandComputer extends ItemComputer
@@ -51,7 +52,7 @@ public class ItemCommandComputer extends ItemComputer
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, @Nonnull CreativeTabs tabs, @Nonnull List list )
     {
         list.add( ComputerItemFactory.create( -1, null, ComputerFamily.Command ) );
     }

src/main/java/dan200/computercraft/shared/computer/items/ItemComputer.java

@@ -21,6 +21,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemComputer extends ItemComputerBase
@@ -71,14 +72,14 @@ public class ItemComputer extends ItemComputerBase
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, @Nonnull CreativeTabs tabs, @Nonnull List list )
     {
         list.add( ComputerItemFactory.create( -1, null, ComputerFamily.Normal ) );
         list.add( ComputerItemFactory.create( -1, null, ComputerFamily.Advanced ) );
     }
 
     @Override
-    public boolean placeBlockAt( ItemStack stack, EntityPlayer player, World world, BlockPos pos, EnumFacing side, float hitX, float hitY, float hitZ, IBlockState newState )
+    public boolean placeBlockAt( @Nonnull ItemStack stack, @Nonnull EntityPlayer player, World world, @Nonnull BlockPos pos, EnumFacing side, float hitX, float hitY, float hitZ, @Nonnull IBlockState newState )
     {
         if( super.placeBlockAt( stack, player, world, pos, side, hitX, hitY, hitZ, newState ) )
         {
@@ -110,6 +111,7 @@ public class ItemComputer extends ItemComputerBase
         }
     }
 
+    @Nonnull
     @Override
     public String getUnlocalizedName( ItemStack stack )
     {

src/main/java/dan200/computercraft/shared/computer/items/ItemComputerBase.java

@@ -18,6 +18,7 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public abstract class ItemComputerBase extends ItemBlock implements IComputerItem, IMedia
@@ -36,7 +37,7 @@ public abstract class ItemComputerBase extends ItemBlock implements IComputerIte
     }
 
     @Override
-    public void addInformation( ItemStack stack, EntityPlayer player, List list, boolean debug )
+    public void addInformation( @Nonnull ItemStack stack, @Nonnull EntityPlayer player, @Nonnull List list, boolean debug )
     {
         if( debug )
         {
@@ -54,7 +55,7 @@ public abstract class ItemComputerBase extends ItemBlock implements IComputerIte
     public abstract int getComputerID( ItemStack stack );
 
     @Override
-    public String getLabel( ItemStack stack )
+    public String getLabel( @Nonnull ItemStack stack )
     {
         if( stack.hasDisplayName() )
         {
@@ -73,7 +74,7 @@ public abstract class ItemComputerBase extends ItemBlock implements IComputerIte
     // IMedia implementation
 
     @Override
-    public boolean setLabel( ItemStack stack, String label )
+    public boolean setLabel( @Nonnull ItemStack stack, String label )
     {
         if( label != null )
         {
@@ -87,19 +88,19 @@ public abstract class ItemComputerBase extends ItemBlock implements IComputerIte
     }
 
     @Override
-    public String getAudioTitle( ItemStack stack )
+    public String getAudioTitle( @Nonnull ItemStack stack )
     {
         return null;
     }
 
     @Override
-    public SoundEvent getAudio( ItemStack stack )
+    public SoundEvent getAudio( @Nonnull ItemStack stack )
     {
         return null;
     }
 
     @Override
-    public IMount createDataMount( ItemStack stack, World world )
+    public IMount createDataMount( @Nonnull ItemStack stack, @Nonnull World world )
     {
         ComputerFamily family = getFamily( stack );
         if( family != ComputerFamily.Command )

src/main/java/dan200/computercraft/shared/media/common/DefaultMediaProvider.java

@@ -7,6 +7,8 @@ import net.minecraft.item.Item;
 import net.minecraft.item.ItemRecord;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+
 public class DefaultMediaProvider implements IMediaProvider
 {
     public DefaultMediaProvider()
@@ -14,7 +16,7 @@ public class DefaultMediaProvider implements IMediaProvider
     }
 
     @Override
-    public IMedia getMedia( ItemStack stack )
+    public IMedia getMedia( @Nonnull ItemStack stack )
     {
         Item item = stack.getItem();
         if( item instanceof IMedia )

src/main/java/dan200/computercraft/shared/media/inventory/ContainerHeldItem.java

@@ -12,6 +12,8 @@ import net.minecraft.inventory.Container;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.EnumHand;
 
+import javax.annotation.Nonnull;
+
 public class ContainerHeldItem extends Container
 {
     private final ItemStack m_stack;
@@ -29,7 +31,7 @@ public class ContainerHeldItem extends Container
     }
 
     @Override
-    public boolean canInteractWith( EntityPlayer player )
+    public boolean canInteractWith( @Nonnull EntityPlayer player )
     {
         if( player != null && player.isEntityAlive() )
         {

src/main/java/dan200/computercraft/shared/media/items/ItemDiskLegacy.java

@@ -20,6 +20,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemDiskLegacy extends Item
@@ -34,7 +35,7 @@ public class ItemDiskLegacy extends Item
     }
     
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, CreativeTabs tabs, List list )
     {
         for( int colour=0; colour<16; ++colour )
         {
@@ -94,7 +95,7 @@ public class ItemDiskLegacy extends Item
     // IMedia implementation
 
     @Override
-    public String getLabel( ItemStack stack )
+    public String getLabel( @Nonnull ItemStack stack )
     {
         if( stack.hasDisplayName() )
         {
@@ -104,7 +105,7 @@ public class ItemDiskLegacy extends Item
     }
     
     @Override
-    public boolean setLabel( ItemStack stack, String label )
+    public boolean setLabel( @Nonnull ItemStack stack, String label )
     {
         if( label != null )
         {
@@ -118,19 +119,19 @@ public class ItemDiskLegacy extends Item
     }
     
     @Override
-    public String getAudioTitle( ItemStack stack )
+    public String getAudioTitle( @Nonnull ItemStack stack )
     {
         return null;
     }
     
     @Override
-    public SoundEvent getAudio( ItemStack stack )
+    public SoundEvent getAudio( @Nonnull ItemStack stack )
     {
         return null;
     }
     
     @Override
-    public IMount createDataMount( ItemStack stack, World world )
+    public IMount createDataMount( @Nonnull ItemStack stack, @Nonnull World world )
     {
         int diskID = getDiskID( stack );
         if( diskID < 0 )

src/main/java/dan200/computercraft/shared/media/items/ItemPrintout.java

@@ -17,6 +17,7 @@ import net.minecraft.util.EnumActionResult;
 import net.minecraft.util.EnumHand;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemPrintout extends Item
@@ -41,7 +42,7 @@ public class ItemPrintout extends Item
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, CreativeTabs tabs, List list )
     {
         list.add( createSingleFromTitleAndText( null, new String[ LINES_PER_PAGE ], new String[ LINES_PER_PAGE ] ) );
         list.add( createMultipleFromTitleAndText( null, new String[ 2*LINES_PER_PAGE ], new String[ 2*LINES_PER_PAGE ] ) );
@@ -58,6 +59,7 @@ public class ItemPrintout extends Item
         }
     }
 
+    @Nonnull
     @Override
     public String getUnlocalizedName( ItemStack stack )
     {
@@ -80,8 +82,9 @@ public class ItemPrintout extends Item
         }
     }
 
+    @Nonnull
     @Override
-    public ActionResult<ItemStack> onItemRightClick( ItemStack stack, World world, EntityPlayer player, EnumHand hand )
+    public ActionResult<ItemStack> onItemRightClick( @Nonnull ItemStack stack, World world, EntityPlayer player, EnumHand hand )
     {
         if( !world.isRemote )
         {

src/main/java/dan200/computercraft/shared/media/items/ItemTreasureDisk.java

@@ -21,6 +21,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -38,7 +39,7 @@ public class ItemTreasureDisk extends Item
     }
     
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, CreativeTabs tabs, List list )
     {
     }
     
@@ -61,31 +62,31 @@ public class ItemTreasureDisk extends Item
     // IMedia implementation
 
     @Override
-    public String getLabel( ItemStack stack )
+    public String getLabel( @Nonnull ItemStack stack )
     {
         return getTitle( stack );
     }
     
     @Override
-    public boolean setLabel( ItemStack stack, String label )
+    public boolean setLabel( @Nonnull ItemStack stack, String label )
     {
         return false;
     }
     
     @Override
-    public String getAudioTitle( ItemStack stack )
+    public String getAudioTitle( @Nonnull ItemStack stack )
     {
         return null;
     }
     
     @Override
-    public SoundEvent getAudio( ItemStack stack )
+    public SoundEvent getAudio( @Nonnull ItemStack stack )
     {
         return null;
     }
     
     @Override
-    public IMount createDataMount( ItemStack stack, World world )
+    public IMount createDataMount( @Nonnull ItemStack stack, @Nonnull World world )
     {
         IMount rootTreasure = getTreasureMount();
         String subPath = getSubPath( stack );

src/main/java/dan200/computercraft/shared/media/items/RecordMedia.java

@@ -15,6 +15,8 @@ import net.minecraft.util.SoundEvent;
 import net.minecraft.world.World;
 import net.minecraftforge.fml.common.ObfuscationReflectionHelper;
 
+import javax.annotation.Nonnull;
+
 // An implementation of IMedia for ItemRecord's
 public class RecordMedia implements IMedia
 {
@@ -23,32 +25,32 @@ public class RecordMedia implements IMedia
     }
      
     @Override
-    public String getLabel( ItemStack stack )
+    public String getLabel( @Nonnull ItemStack stack )
     {
         return getAudioTitle( stack );
     }
     
     @Override
-    public boolean setLabel( ItemStack stack, String label )
+    public boolean setLabel( @Nonnull ItemStack stack, String label )
     {
         return false;
     }
     
     @Override
-    public String getAudioTitle( ItemStack stack )
+    public String getAudioTitle( @Nonnull ItemStack stack )
     {
         return ComputerCraft.getRecordInfo( stack );
     }
     
     @Override
-    public SoundEvent getAudio( ItemStack stack )
+    public SoundEvent getAudio( @Nonnull ItemStack stack )
     {
         ItemRecord itemRecord = (ItemRecord)stack.getItem();
         return ObfuscationReflectionHelper.getPrivateValue(ItemRecord.class, itemRecord, "field_185076_b");
     }
     
     @Override
-    public IMount createDataMount( ItemStack stack, World world )
+    public IMount createDataMount( @Nonnull ItemStack stack, @Nonnull World world )
     {
         return null;
     }

src/main/java/dan200/computercraft/shared/media/recipes/DiskRecipe.java

@@ -14,6 +14,8 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.item.crafting.IRecipe;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class DiskRecipe implements IRecipe
 {
     public DiskRecipe()
@@ -21,7 +23,7 @@ public class DiskRecipe implements IRecipe
     }
 
     @Override
-    public boolean matches( InventoryCrafting inventory, World world )
+    public boolean matches( @Nonnull InventoryCrafting inventory, @Nonnull World world )
     {
         boolean diskFound = false;
         boolean paperFound = false;
@@ -75,7 +77,7 @@ public class DiskRecipe implements IRecipe
     }
 
     @Override
-    public ItemStack getCraftingResult(InventoryCrafting par1InventoryCrafting)
+    public ItemStack getCraftingResult( @Nonnull InventoryCrafting par1InventoryCrafting)
     {
         int diskID = -1;
         String diskLabel = null;
@@ -153,8 +155,9 @@ public class DiskRecipe implements IRecipe
         return ItemDiskLegacy.createFromIDAndColour( -1, null, Colour.Blue.getHex() );
     }
 
+    @Nonnull
     @Override
-    public ItemStack[] getRemainingItems( InventoryCrafting inventoryCrafting )
+    public ItemStack[] getRemainingItems( @Nonnull InventoryCrafting inventoryCrafting )
     {
         ItemStack[] results = new ItemStack[ inventoryCrafting.getSizeInventory() ];
         for (int i = 0; i < results.length; ++i)

src/main/java/dan200/computercraft/shared/media/recipes/PrintoutRecipe.java

@@ -14,6 +14,8 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.item.crafting.IRecipe;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class PrintoutRecipe implements IRecipe
 {
     public PrintoutRecipe( )
@@ -33,13 +35,13 @@ public class PrintoutRecipe implements IRecipe
     }
 
     @Override
-    public boolean matches( InventoryCrafting _inventory, World world )
+    public boolean matches( @Nonnull InventoryCrafting _inventory, @Nonnull World world )
     {
         return (getCraftingResult( _inventory ) != null);
     }
 
     @Override
-    public ItemStack getCraftingResult( InventoryCrafting inventory )
+    public ItemStack getCraftingResult( @Nonnull InventoryCrafting inventory )
     {
         // See if we match the recipe, and extract the input disk ID and dye colour
         int numPages = 0;
@@ -146,8 +148,9 @@ public class PrintoutRecipe implements IRecipe
         return null;
     }
 
+    @Nonnull
     @Override
-    public ItemStack[] getRemainingItems( InventoryCrafting inventoryCrafting )
+    public ItemStack[] getRemainingItems( @Nonnull InventoryCrafting inventoryCrafting )
     {
         ItemStack[] results = new ItemStack[ inventoryCrafting.getSizeInventory() ];
         for (int i = 0; i < results.length; ++i)

src/main/java/dan200/computercraft/shared/peripheral/PeripheralType.java

@@ -8,6 +8,8 @@ package dan200.computercraft.shared.peripheral;
 
 import net.minecraft.util.IStringSerializable;
 
+import javax.annotation.Nonnull;
+
 public enum PeripheralType implements IStringSerializable
 {
     DiskDrive( "disk_drive" ),
@@ -27,6 +29,7 @@ public enum PeripheralType implements IStringSerializable
         m_name = name;
     }
 
+    @Nonnull
     @Override
     public String getName()
     {

src/main/java/dan200/computercraft/shared/peripheral/commandblock/CommandBlockPeripheral.java

@@ -14,6 +14,8 @@ import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.tileentity.TileEntityCommandBlock;
 import net.minecraft.util.math.BlockPos;
 
+import javax.annotation.Nonnull;
+
 public class CommandBlockPeripheral implements IPeripheral
 {
     private final TileEntityCommandBlock m_commandBlock;
@@ -25,12 +27,14 @@ public class CommandBlockPeripheral implements IPeripheral
 
     // IPeripheral methods
 
+    @Nonnull
     @Override
     public String getType()
     {
         return "command";
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -42,7 +46,7 @@ public class CommandBlockPeripheral implements IPeripheral
     }
 
     @Override
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, final Object[] arguments ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull final Object[] arguments ) throws LuaException, InterruptedException
     {
         switch (method)
         {
@@ -108,12 +112,12 @@ public class CommandBlockPeripheral implements IPeripheral
     }
 
     @Override
-    public void attach( IComputerAccess computer )
+    public void attach( @Nonnull IComputerAccess computer )
     {    
     }
 
     @Override
-    public void detach( IComputerAccess computer )
+    public void detach( @Nonnull IComputerAccess computer )
     {
     }
 

src/main/java/dan200/computercraft/shared/peripheral/commandblock/CommandBlockPeripheralProvider.java

@@ -14,10 +14,12 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class CommandBlockPeripheralProvider implements IPeripheralProvider
 {
     @Override
-    public IPeripheral getPeripheral( World world, BlockPos pos, EnumFacing side )
+    public IPeripheral getPeripheral( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null && tile instanceof TileEntityCommandBlock )

src/main/java/dan200/computercraft/shared/peripheral/common/BlockCable.java

@@ -21,6 +21,8 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.IBlockAccess;
 
+import javax.annotation.Nonnull;
+
 public class BlockCable extends BlockPeripheralBase
 {
     // Statics
@@ -73,6 +75,7 @@ public class BlockCable extends BlockPeripheralBase
         );
     }
 
+    @Nonnull
     @Override
     protected BlockStateContainer createBlockState()
     {
@@ -88,6 +91,7 @@ public class BlockCable extends BlockPeripheralBase
         });
     }
 
+    @Nonnull
     @Override
     public IBlockState getStateFromMeta( int meta )
     {
@@ -174,8 +178,9 @@ public class BlockCable extends BlockPeripheralBase
         }
     }
 
+    @Nonnull
     @Override
-    public IBlockState getActualState( IBlockState state, IBlockAccess world, BlockPos pos )
+    public IBlockState getActualState( @Nonnull IBlockState state, IBlockAccess world, BlockPos pos )
     {
         state = state.withProperty( Properties.NORTH, doesConnect( state, world, pos, EnumFacing.NORTH ) );
         state = state.withProperty( Properties.SOUTH, doesConnect( state, world, pos, EnumFacing.SOUTH ) );
@@ -209,7 +214,7 @@ public class BlockCable extends BlockPeripheralBase
     }
 
     @Override
-    public boolean shouldSideBeRendered( IBlockState state, IBlockAccess world, BlockPos pos, EnumFacing side )
+    public boolean shouldSideBeRendered( IBlockState state, @Nonnull IBlockAccess world, @Nonnull BlockPos pos, EnumFacing side )
     {
         return true;
     }

src/main/java/dan200/computercraft/shared/peripheral/common/BlockCableModemVariant.java

@@ -9,6 +9,8 @@ package dan200.computercraft.shared.peripheral.common;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.util.IStringSerializable;
 
+import javax.annotation.Nonnull;
+
 public enum BlockCableModemVariant implements IStringSerializable
 {
     None( "none", null ),
@@ -60,6 +62,7 @@ public enum BlockCableModemVariant implements IStringSerializable
         m_facing = facing;
     }
 
+    @Nonnull
     @Override
     public String getName()
     {

src/main/java/dan200/computercraft/shared/peripheral/common/BlockPeripheral.java

@@ -30,6 +30,8 @@ import net.minecraft.world.World;
 import net.minecraftforge.fml.relauncher.Side;
 import net.minecraftforge.fml.relauncher.SideOnly;
 
+import javax.annotation.Nonnull;
+
 public class BlockPeripheral extends BlockPeripheralBase
 {
     public static class Properties
@@ -49,12 +51,14 @@ public class BlockPeripheral extends BlockPeripheralBase
         );
     }
 
+    @Nonnull
     @SideOnly( Side.CLIENT)
     public BlockRenderLayer getBlockLayer()
     {
         return BlockRenderLayer.CUTOUT;
     }
 
+    @Nonnull
     @Override
     protected BlockStateContainer createBlockState()
     {
@@ -64,6 +68,7 @@ public class BlockPeripheral extends BlockPeripheralBase
         });
     }
 
+    @Nonnull
     @Override
     public IBlockState getStateFromMeta( int meta )
     {
@@ -166,8 +171,9 @@ public class BlockPeripheral extends BlockPeripheralBase
         return meta;
     }
 
+    @Nonnull
     @Override
-    public IBlockState getActualState( IBlockState state, IBlockAccess world, BlockPos pos )
+    public IBlockState getActualState( @Nonnull IBlockState state, IBlockAccess world, BlockPos pos )
     {
         int anim;
         EnumFacing dir;

src/main/java/dan200/computercraft/shared/peripheral/common/BlockPeripheralBase.java

@@ -17,6 +17,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public abstract class BlockPeripheralBase extends BlockDirectional
 {
     public BlockPeripheralBase()
@@ -42,7 +44,7 @@ public abstract class BlockPeripheralBase extends BlockDirectional
     }
 
     @Override
-    public final boolean canPlaceBlockOnSide( World world, BlockPos pos, EnumFacing side )
+    public final boolean canPlaceBlockOnSide( @Nonnull World world, @Nonnull BlockPos pos, EnumFacing side )
     {
         return true; // ItemPeripheralBase handles this
     }

src/main/java/dan200/computercraft/shared/peripheral/common/BlockPeripheralVariant.java

@@ -9,6 +9,8 @@ package dan200.computercraft.shared.peripheral.common;
 import dan200.computercraft.shared.peripheral.PeripheralType;
 import net.minecraft.util.IStringSerializable;
 
+import javax.annotation.Nonnull;
+
 public enum BlockPeripheralVariant implements IStringSerializable
 {
     DiskDriveEmpty( "disk_drive_empty", PeripheralType.DiskDrive ),
@@ -130,6 +132,7 @@ public enum BlockPeripheralVariant implements IStringSerializable
         m_peripheralType = peripheralType;
     }
 
+    @Nonnull
     @Override
     public String getName()
     {

src/main/java/dan200/computercraft/shared/peripheral/common/DefaultPeripheralProvider.java

@@ -16,6 +16,8 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class DefaultPeripheralProvider implements IPeripheralProvider
 {
     public DefaultPeripheralProvider()
@@ -23,7 +25,7 @@ public class DefaultPeripheralProvider implements IPeripheralProvider
     }
 
     @Override
-    public IPeripheral getPeripheral( World world, BlockPos pos, EnumFacing side )
+    public IPeripheral getPeripheral( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile != null )

src/main/java/dan200/computercraft/shared/peripheral/common/ItemAdvancedModem.java

@@ -13,6 +13,7 @@ import net.minecraft.creativetab.CreativeTabs;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemAdvancedModem extends ItemPeripheralBase
@@ -48,7 +49,7 @@ public class ItemAdvancedModem extends ItemPeripheralBase
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, @Nonnull CreativeTabs tabs, @Nonnull List list )
     {
         list.add( PeripheralItemFactory.create( PeripheralType.AdvancedModem, null, 1 ) );
     }

src/main/java/dan200/computercraft/shared/peripheral/common/ItemCable.java

@@ -24,6 +24,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemCable extends ItemPeripheralBase
@@ -63,14 +64,15 @@ public class ItemCable extends ItemPeripheralBase
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, @Nonnull CreativeTabs tabs, @Nonnull List list )
     {
         list.add( PeripheralItemFactory.create( PeripheralType.WiredModem, null, 1 ) );
         list.add( PeripheralItemFactory.create( PeripheralType.Cable, null, 1 ) );
     }
 
+    @Nonnull
     @Override
-    public EnumActionResult onItemUse( ItemStack stack, EntityPlayer player, World world, BlockPos pos, EnumHand hand, EnumFacing side, float fx, float fy, float fz )
+    public EnumActionResult onItemUse( ItemStack stack, @Nonnull EntityPlayer player, World world, @Nonnull BlockPos pos, EnumHand hand, @Nonnull EnumFacing side, float fx, float fy, float fz )
     {
         if( !canPlaceBlockOnSide( world, pos, side, player, stack ) )
         {

src/main/java/dan200/computercraft/shared/peripheral/common/ItemPeripheral.java

@@ -13,6 +13,7 @@ import net.minecraft.creativetab.CreativeTabs;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemPeripheral extends ItemPeripheralBase
@@ -68,7 +69,7 @@ public class ItemPeripheral extends ItemPeripheralBase
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List list )
+    public void getSubItems( @Nonnull Item itemID, @Nonnull CreativeTabs tabs, @Nonnull List list )
     {
         list.add( PeripheralItemFactory.create( PeripheralType.DiskDrive, null, 1 ) );
         list.add( PeripheralItemFactory.create( PeripheralType.Printer, null, 1 ) );

src/main/java/dan200/computercraft/shared/peripheral/common/ItemPeripheralBase.java

@@ -15,6 +15,8 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public abstract class ItemPeripheralBase extends ItemBlock implements IPeripheralItem
 {
     protected ItemPeripheralBase( Block block )
@@ -33,7 +35,7 @@ public abstract class ItemPeripheralBase extends ItemBlock implements IPeriphera
     }
 
     @Override
-    public boolean canPlaceBlockOnSide( World world, BlockPos pos, EnumFacing side, EntityPlayer player, ItemStack stack ) // canPlaceItemBlockOnSide
+    public boolean canPlaceBlockOnSide( World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side, EntityPlayer player, @Nonnull ItemStack stack ) // canPlaceItemBlockOnSide
     {
         PeripheralType type = getPeripheralType( stack );
         switch( type )
@@ -55,6 +57,7 @@ public abstract class ItemPeripheralBase extends ItemBlock implements IPeriphera
         }
     }
 
+    @Nonnull
     @Override
     public String getUnlocalizedName( ItemStack stack )
     {

src/main/java/dan200/computercraft/shared/peripheral/common/TilePeripheralBase.java

@@ -15,6 +15,7 @@ import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.ITickable;
 import net.minecraft.util.EnumFacing;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public abstract class TilePeripheralBase extends TileGeneric
@@ -45,7 +46,7 @@ public abstract class TilePeripheralBase extends TileGeneric
     }
 
     @Override
-    public void getDroppedItems( List<ItemStack> drops, boolean creative )
+    public void getDroppedItems( @Nonnull List<ItemStack> drops, boolean creative )
     {
         if( !creative )
         {
@@ -149,6 +150,7 @@ public abstract class TilePeripheralBase extends TileGeneric
         }
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT( NBTTagCompound nbttagcompound )
     {
@@ -164,7 +166,7 @@ public abstract class TilePeripheralBase extends TileGeneric
     }
 
     @Override
-    public void readDescription( NBTTagCompound nbttagcompound )
+    public void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         m_dir = EnumFacing.getFront( nbttagcompound.getInteger( "dir" ) );
@@ -180,7 +182,7 @@ public abstract class TilePeripheralBase extends TileGeneric
     }
 
     @Override
-    public void writeDescription( NBTTagCompound nbttagcompound )
+    public void writeDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.writeDescription( nbttagcompound );
         nbttagcompound.setInteger( "dir", m_dir.getIndex() );

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/ContainerDiskDrive.java

@@ -12,6 +12,8 @@ import net.minecraft.inventory.IInventory;
 import net.minecraft.inventory.Slot;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+
 public class ContainerDiskDrive extends Container
 {
     private final TileDiskDrive m_diskDrive;
@@ -36,7 +38,7 @@ public class ContainerDiskDrive extends Container
     }
 
     @Override
-    public boolean canInteractWith( EntityPlayer player )
+    public boolean canInteractWith( @Nonnull EntityPlayer player )
     {
         return m_diskDrive.isUseableByPlayer( player );
     }

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/DiskDrivePeripheral.java

@@ -16,6 +16,8 @@ import dan200.computercraft.shared.util.StringUtil;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+
 public class DiskDrivePeripheral implements IPeripheral
 {
     private final TileDiskDrive m_diskDrive;
@@ -25,12 +27,14 @@ public class DiskDrivePeripheral implements IPeripheral
         m_diskDrive = diskDrive;
     }
 
+    @Nonnull
     @Override
     public String getType()
     {
         return "drive";
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -50,7 +54,7 @@ public class DiskDrivePeripheral implements IPeripheral
     }
 
     @Override
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object[] arguments ) throws LuaException
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -174,13 +178,13 @@ public class DiskDrivePeripheral implements IPeripheral
     }
 
     @Override
-    public void attach( IComputerAccess computer )
+    public void attach( @Nonnull IComputerAccess computer )
     {
         m_diskDrive.mount( computer );
     }
 
     @Override
-    public void detach( IComputerAccess computer )
+    public void detach( @Nonnull IComputerAccess computer )
     {
         m_diskDrive.unmount( computer );
     }

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/TileDiskDrive.java

@@ -29,6 +29,7 @@ import net.minecraft.util.math.*;
 import net.minecraft.util.text.*;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
@@ -145,6 +146,7 @@ public class TileDiskDrive extends TilePeripheralBase
         }
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT(NBTTagCompound nbttagcompound)
     {
@@ -320,6 +322,7 @@ public class TileDiskDrive extends TilePeripheralBase
         return getLabel() != null;
     }
 
+    @Nonnull
     @Override
     public String getName()
     {
@@ -334,6 +337,7 @@ public class TileDiskDrive extends TilePeripheralBase
         }
     }
 
+    @Nonnull
     @Override
     public ITextComponent getDisplayName()
     {
@@ -354,23 +358,23 @@ public class TileDiskDrive extends TilePeripheralBase
     }
 
     @Override
-    public void openInventory( EntityPlayer player )
+    public void openInventory( @Nonnull EntityPlayer player )
     {
     }
     
     @Override
-    public void closeInventory( EntityPlayer player )
+    public void closeInventory( @Nonnull EntityPlayer player )
     {
     }
 
     @Override
-    public boolean isItemValidForSlot(int i, ItemStack itemstack)
+    public boolean isItemValidForSlot( int i, @Nonnull ItemStack itemstack)
     {
         return true;
     }
 
     @Override
-    public boolean isUseableByPlayer( EntityPlayer player )
+    public boolean isUseableByPlayer( @Nonnull EntityPlayer player )
     {
         return isUsable( player, false );
     }
@@ -613,7 +617,7 @@ public class TileDiskDrive extends TilePeripheralBase
     }
 
     @Override
-    public final void readDescription( NBTTagCompound nbttagcompound )
+    public final void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         if( nbttagcompound.hasKey( "item" ) )
@@ -628,7 +632,7 @@ public class TileDiskDrive extends TilePeripheralBase
     }
 
     @Override
-    public void writeDescription( NBTTagCompound nbttagcompound )
+    public void writeDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.writeDescription( nbttagcompound );
         if( m_diskStack != null )
@@ -659,7 +663,7 @@ public class TileDiskDrive extends TilePeripheralBase
     }
 
     @Override
-    public boolean shouldRefresh( World world, BlockPos pos, IBlockState oldState, IBlockState newState )
+    public boolean shouldRefresh( World world, BlockPos pos, @Nonnull IBlockState oldState, @Nonnull IBlockState newState )
     {
         return super.shouldRefresh( world, pos, oldState, newState ) || ComputerCraft.Blocks.peripheral.getPeripheralType( newState ) != PeripheralType.DiskDrive;
     }

src/main/java/dan200/computercraft/shared/peripheral/modem/BlockAdvancedModem.java

@@ -23,6 +23,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class BlockAdvancedModem extends BlockPeripheralBase
 {
     public static class Properties
@@ -42,6 +44,7 @@ public class BlockAdvancedModem extends BlockPeripheralBase
         );
     }
 
+    @Nonnull
     @Override
     protected BlockStateContainer createBlockState()
     {
@@ -51,6 +54,7 @@ public class BlockAdvancedModem extends BlockPeripheralBase
         });
     }
 
+    @Nonnull
     @Override
     public IBlockState getStateFromMeta( int meta )
     {
@@ -63,12 +67,13 @@ public class BlockAdvancedModem extends BlockPeripheralBase
     @Override
     public int getMetaFromState( IBlockState state )
     {
-        EnumFacing dir = (EnumFacing) state.getValue( Properties.FACING );
+        EnumFacing dir = state.getValue( Properties.FACING );
         return dir.getIndex();
     }
 
+    @Nonnull
     @Override
-    public IBlockState getActualState( IBlockState state, IBlockAccess world, BlockPos pos )
+    public IBlockState getActualState( @Nonnull IBlockState state, IBlockAccess world, BlockPos pos )
     {
         int anim;
         EnumFacing dir;

src/main/java/dan200/computercraft/shared/peripheral/modem/ModemPeripheral.java

@@ -13,6 +13,7 @@ import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
@@ -203,12 +204,14 @@ public abstract class ModemPeripheral
     
     // IPeripheral implementation
 
+    @Nonnull
     @Override
     public String getType()
     {
         return "modem";
     }
        
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -237,7 +240,7 @@ public abstract class ModemPeripheral
     }
     
     @Override
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
     {
         switch( method )
         {
@@ -366,7 +369,7 @@ public abstract class ModemPeripheral
     }
     
     @Override
-    public synchronized void attach( IComputerAccess computer )
+    public synchronized void attach( @Nonnull IComputerAccess computer )
     {
         m_computer = computer;
         setNetwork( getNetwork() );
@@ -374,7 +377,7 @@ public abstract class ModemPeripheral
     }
     
     @Override
-    public synchronized void detach( IComputerAccess computer )
+    public synchronized void detach( @Nonnull IComputerAccess computer )
     {
         if( m_network != null )
         {

src/main/java/dan200/computercraft/shared/peripheral/modem/TileCable.java

@@ -31,6 +31,7 @@ import net.minecraft.util.math.*;
 import net.minecraft.util.text.*;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.io.File;
 import java.util.*;
 
@@ -93,6 +94,7 @@ public class TileCable extends TileModemBase
             return new Vec3d( (double)pos.getX() + 0.5, (double)pos.getY() + 0.5, (double)pos.getZ() + 0.5 );
         }
 
+        @Nonnull
         @Override
         public String[] getMethodNames()
         {
@@ -117,7 +119,7 @@ public class TileCable extends TileModemBase
         }
 
         @Override
-        public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException
+        public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
         {
             String[] methods = super.getMethodNames();
             switch( method - methods.length )
@@ -186,7 +188,7 @@ public class TileCable extends TileModemBase
         }
 
         @Override
-        public void attach( IComputerAccess computer )
+        public void attach( @Nonnull IComputerAccess computer )
         {
             super.attach( computer );
             synchronized( m_entity.m_peripheralsByName )
@@ -205,7 +207,7 @@ public class TileCable extends TileModemBase
         }
 
         @Override
-        public synchronized void detach( IComputerAccess computer )
+        public synchronized void detach( @Nonnull IComputerAccess computer )
         {
             synchronized( m_entity.m_peripheralsByName )
             {
@@ -302,7 +304,7 @@ public class TileCable extends TileModemBase
     }
 
     @Override
-    public void getDroppedItems( List<ItemStack> drops, boolean creative )
+    public void getDroppedItems( @Nonnull List<ItemStack> drops, boolean creative )
     {
         if( !creative )
         {
@@ -409,6 +411,7 @@ public class TileCable extends TileModemBase
         return new AxisAlignedBB( xMin, yMin, zMin, xMax, yMax, zMax );
     }
     
+    @Nonnull
     @Override
     public AxisAlignedBB getBounds()
     {
@@ -434,7 +437,7 @@ public class TileCable extends TileModemBase
     }
 
     @Override
-    public void getCollisionBounds( List<AxisAlignedBB> bounds )
+    public void getCollisionBounds( @Nonnull List<AxisAlignedBB> bounds )
     {
         PeripheralType type = getPeripheralType();
         if( type == PeripheralType.WiredModem || type == PeripheralType.WiredModemWithCable )
@@ -503,6 +506,7 @@ public class TileCable extends TileModemBase
         m_attachedPeripheralID = nbttagcompound.getInteger( "peripheralID" );
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT(NBTTagCompound nbttagcompound)
     {
@@ -828,25 +832,25 @@ public class TileCable extends TileModemBase
         // IComputerAccess implementation
 
         @Override
-        public String mount( String desiredLocation, IMount mount )
+        public String mount( @Nonnull String desiredLocation, @Nonnull IMount mount )
         {
             return m_computer.mount( desiredLocation, mount, m_name );
         }
 
         @Override
-        public String mount( String desiredLocation, IMount mount, String driveName )
+        public String mount( @Nonnull String desiredLocation, @Nonnull IMount mount, @Nonnull String driveName )
         {
             return m_computer.mount( desiredLocation, mount, driveName );
         }
 
         @Override
-        public String mountWritable( String desiredLocation, IWritableMount mount )
+        public String mountWritable( @Nonnull String desiredLocation, @Nonnull IWritableMount mount )
         {
             return m_computer.mountWritable( desiredLocation, mount, m_name );
         }
 
         @Override
-        public String mountWritable( String desiredLocation, IWritableMount mount, String driveName )
+        public String mountWritable( @Nonnull String desiredLocation, @Nonnull IWritableMount mount, @Nonnull String driveName )
         {
             return m_computer.mountWritable( desiredLocation, mount, driveName );
         }
@@ -864,11 +868,12 @@ public class TileCable extends TileModemBase
         }
         
         @Override
-        public void queueEvent( String event, Object[] arguments )
+        public void queueEvent( @Nonnull String event, Object[] arguments )
         {
             m_computer.queueEvent( event, arguments );
         }
         
+        @Nonnull
         @Override
         public String getAttachmentName()
         {

src/main/java/dan200/computercraft/shared/peripheral/modem/TileModemBase.java

@@ -14,6 +14,8 @@ import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.AxisAlignedBB;
 
+import javax.annotation.Nonnull;
+
 public abstract class TileModemBase extends TilePeripheralBase
 {
     private static final AxisAlignedBB[] BOXES = new AxisAlignedBB[] {
@@ -65,6 +67,7 @@ public abstract class TileModemBase extends TilePeripheralBase
         }
     }
 
+    @Nonnull
     @Override
     public AxisAlignedBB getBounds()
     {
@@ -95,7 +98,7 @@ public abstract class TileModemBase extends TilePeripheralBase
     }
 
     @Override
-    public final void readDescription( NBTTagCompound nbttagcompound )
+    public final void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         updateBlock();

src/main/java/dan200/computercraft/shared/peripheral/modem/TileWirelessModem.java

@@ -17,6 +17,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class TileWirelessModem extends TileModemBase
 {
     // Statics
@@ -120,7 +122,7 @@ public class TileWirelessModem extends TileModemBase
     }
 
     @Override
-    public boolean shouldRefresh( World world, BlockPos pos, IBlockState oldState, IBlockState newState )
+    public boolean shouldRefresh( World world, BlockPos pos, @Nonnull IBlockState oldState, @Nonnull IBlockState newState )
     {
         return super.shouldRefresh( world, pos, oldState, newState ) || ComputerCraft.Blocks.peripheral.getPeripheralType( newState ) != PeripheralType.WirelessModem;
     }

src/main/java/dan200/computercraft/shared/peripheral/monitor/MonitorPeripheral.java

@@ -12,6 +12,8 @@ import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.terminal.Terminal;
 
+import javax.annotation.Nonnull;
+
 public class MonitorPeripheral implements IPeripheral
 {
     private final TileMonitor m_monitor;
@@ -23,12 +25,14 @@ public class MonitorPeripheral implements IPeripheral
 
     // IPeripheral implementation
 
+    @Nonnull
     @Override
     public String getType()
     {
         return "monitor";
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -57,7 +61,7 @@ public class MonitorPeripheral implements IPeripheral
     }
 
     @Override
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object args[] ) throws LuaException
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object args[] ) throws LuaException
     {
         switch( method )
         {
@@ -223,13 +227,13 @@ public class MonitorPeripheral implements IPeripheral
     }
 
     @Override
-    public void attach( IComputerAccess computer )
+    public void attach( @Nonnull IComputerAccess computer )
     {
         m_monitor.addComputer( computer );
     }
 
     @Override
-    public void detach( IComputerAccess computer )
+    public void detach( @Nonnull IComputerAccess computer )
     {
         m_monitor.removeComputer( computer );
     }

src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java

@@ -25,6 +25,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -111,6 +112,7 @@ public class TileMonitor extends TilePeripheralBase
         return false;
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT( NBTTagCompound nbttagcompound )
     {
@@ -206,7 +208,7 @@ public class TileMonitor extends TilePeripheralBase
     // Networking stuff
 
     @Override
-    public void writeDescription( NBTTagCompound nbttagcompound )
+    public void writeDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.writeDescription( nbttagcompound );
         nbttagcompound.setInteger( "xIndex", m_xIndex );
@@ -219,7 +221,7 @@ public class TileMonitor extends TilePeripheralBase
     }
 
     @Override
-    public final void readDescription( NBTTagCompound nbttagcompound )
+    public final void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
 
@@ -815,6 +817,7 @@ public class TileMonitor extends TilePeripheralBase
         }
     }
     
+    @Nonnull
     @Override
     public AxisAlignedBB getRenderBoundingBox()
     {
@@ -840,7 +843,7 @@ public class TileMonitor extends TilePeripheralBase
     }
 
     @Override
-    public boolean shouldRefresh( World world, BlockPos pos, IBlockState oldState, IBlockState newState )
+    public boolean shouldRefresh( World world, BlockPos pos, @Nonnull IBlockState oldState, @Nonnull IBlockState newState )
     {
         if( super.shouldRefresh( world, pos, oldState, newState ) )
         {

src/main/java/dan200/computercraft/shared/peripheral/printer/ContainerPrinter.java

@@ -14,6 +14,8 @@ import net.minecraft.inventory.IInventory;
 import net.minecraft.inventory.Slot;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+
 public class ContainerPrinter extends Container
 {
     private TilePrinter m_printer;
@@ -97,7 +99,7 @@ public class ContainerPrinter extends Container
     }
 
     @Override
-    public boolean canInteractWith( EntityPlayer player )
+    public boolean canInteractWith( @Nonnull EntityPlayer player )
     {
         return m_printer.isUseableByPlayer( player );
     }

src/main/java/dan200/computercraft/shared/peripheral/printer/PrinterPeripheral.java

@@ -12,6 +12,8 @@ import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.terminal.Terminal;
 
+import javax.annotation.Nonnull;
+
 public class PrinterPeripheral implements IPeripheral
 {
     private final TilePrinter m_printer;
@@ -21,12 +23,14 @@ public class PrinterPeripheral implements IPeripheral
         m_printer = printer;
     }
 
+    @Nonnull
     @Override
     public String getType()
     {
         return "printer";
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -44,7 +48,7 @@ public class PrinterPeripheral implements IPeripheral
     }
 
     @Override
-    public Object[] callMethod( IComputerAccess computer, ILuaContext context, int method, Object[] args ) throws LuaException
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -139,12 +143,12 @@ public class PrinterPeripheral implements IPeripheral
     }
 
     @Override
-    public void attach( IComputerAccess computer )
+    public void attach( @Nonnull IComputerAccess computer )
     {
     }
 
     @Override
-    public void detach( IComputerAccess computer )
+    public void detach( @Nonnull IComputerAccess computer )
     {
     }
 

src/main/java/dan200/computercraft/shared/peripheral/printer/TilePrinter.java

@@ -29,6 +29,8 @@ import net.minecraft.util.text.*;
 import net.minecraft.world.World;
 import net.minecraftforge.common.util.Constants;
 
+import javax.annotation.Nonnull;
+
 public class TilePrinter extends TilePeripheralBase
     implements IInventory, ISidedInventory
 {
@@ -102,6 +104,7 @@ public class TilePrinter extends TilePeripheralBase
         }
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT(NBTTagCompound nbttagcompound)
     {
@@ -136,14 +139,14 @@ public class TilePrinter extends TilePeripheralBase
     }
 
     @Override
-    public final void readDescription( NBTTagCompound nbttagcompound )
+    public final void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         updateBlock();
     }
 
     @Override
-    public boolean shouldRefresh( World world, BlockPos pos, IBlockState oldState, IBlockState newState )
+    public boolean shouldRefresh( World world, BlockPos pos, @Nonnull IBlockState oldState, @Nonnull IBlockState newState )
     {
         return super.shouldRefresh( world, pos, oldState, newState ) || ComputerCraft.Blocks.peripheral.getPeripheralType( newState ) != PeripheralType.Printer;
     }
@@ -243,6 +246,7 @@ public class TilePrinter extends TilePeripheralBase
         return getLabel() != null;
     }
 
+    @Nonnull
     @Override
     public String getName()
     {
@@ -257,6 +261,7 @@ public class TilePrinter extends TilePeripheralBase
         }
     }
 
+    @Nonnull
     @Override
     public ITextComponent getDisplayName()
     {
@@ -277,23 +282,23 @@ public class TilePrinter extends TilePeripheralBase
     }
 
     @Override    
-    public void openInventory( EntityPlayer player )
+    public void openInventory( @Nonnull EntityPlayer player )
     {
     }
     
     @Override    
-    public void closeInventory( EntityPlayer player )
+    public void closeInventory( @Nonnull EntityPlayer player )
     {
     }
 
     @Override
-    public boolean isItemValidForSlot( int slot, ItemStack itemstack )
+    public boolean isItemValidForSlot( int slot, @Nonnull ItemStack itemstack )
     {
         return true;
     }
 
     @Override
-    public boolean isUseableByPlayer( EntityPlayer player )
+    public boolean isUseableByPlayer( @Nonnull EntityPlayer player )
     {
         return isUsable( player, false );
     }
@@ -317,8 +322,9 @@ public class TilePrinter extends TilePeripheralBase
 
     // ISidedInventory implementation
     
+    @Nonnull
     @Override
-    public int[] getSlotsForFace( EnumFacing side )
+    public int[] getSlotsForFace( @Nonnull EnumFacing side )
     {
         switch( side )
         {
@@ -329,13 +335,13 @@ public class TilePrinter extends TilePeripheralBase
     }
     
     @Override
-    public boolean canInsertItem( int slot, ItemStack itemstack, EnumFacing face )
+    public boolean canInsertItem( int slot, @Nonnull ItemStack itemstack, @Nonnull EnumFacing face )
     {
         return isItemValidForSlot( slot, itemstack );
     }
 
     @Override
-    public boolean canExtractItem( int slot, ItemStack itemstack, EnumFacing face )
+    public boolean canExtractItem( int slot, @Nonnull ItemStack itemstack, @Nonnull EnumFacing face )
     {
         return true;
     }

src/main/java/dan200/computercraft/shared/pocket/apis/PocketAPI.java

@@ -19,6 +19,8 @@ import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.entity.player.InventoryPlayer;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+
 public class PocketAPI implements ILuaAPI
 {
     private final PocketServerComputer m_computer;
@@ -51,6 +53,7 @@ public class PocketAPI implements ILuaAPI
     {
     }
 
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -61,7 +64,7 @@ public class PocketAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] arguments ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/shared/pocket/items/ItemPocketComputer.java

@@ -35,6 +35,7 @@ import net.minecraftforge.common.util.Constants;
 import net.minecraftforge.fml.relauncher.Side;
 import net.minecraftforge.fml.relauncher.SideOnly;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class ItemPocketComputer extends Item implements IComputerItem, IMedia
@@ -79,7 +80,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
     }
 
     @Override
-    public void getSubItems( Item itemID, CreativeTabs tabs, List<ItemStack> list )
+    public void getSubItems( @Nonnull Item itemID, CreativeTabs tabs, List list )
     {
         getSubItems( list, ComputerFamily.Normal );
         getSubItems( list, ComputerFamily.Advanced );
@@ -151,8 +152,9 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
         }
     }
 
+    @Nonnull
     @Override
-    public ActionResult<ItemStack> onItemRightClick( ItemStack stack, World world, EntityPlayer player, EnumHand hand )
+    public ActionResult<ItemStack> onItemRightClick( @Nonnull ItemStack stack, World world, EntityPlayer player, EnumHand hand )
     {
         if( !world.isRemote )
         {
@@ -176,6 +178,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
         return new ActionResult<ItemStack>( EnumActionResult.SUCCESS, stack );
     }
 
+    @Nonnull
     @Override
     public String getUnlocalizedName( ItemStack stack )
     {
@@ -193,8 +196,9 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
         }
     }
 
+    @Nonnull
     @Override
-    public String getItemStackDisplayName( ItemStack stack )
+    public String getItemStackDisplayName( @Nonnull ItemStack stack )
     {
         String baseString = getUnlocalizedName( stack );
         IPocketUpgrade upgrade = getUpgrade( stack );
@@ -331,7 +335,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
     }
 
     @Override
-    public String getLabel( ItemStack stack )
+    public String getLabel( @Nonnull ItemStack stack )
     {
         if( stack.hasDisplayName() )
         {
@@ -361,7 +365,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
     // IMedia
 
     @Override
-    public boolean setLabel( ItemStack stack, String label )
+    public boolean setLabel( @Nonnull ItemStack stack, String label )
     {
         if( label != null )
         {
@@ -375,19 +379,19 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia
     }
 
     @Override
-    public String getAudioTitle( ItemStack stack )
+    public String getAudioTitle( @Nonnull ItemStack stack )
     {
         return null;
     }
 
     @Override
-    public SoundEvent getAudio( ItemStack stack )
+    public SoundEvent getAudio( @Nonnull ItemStack stack )
     {
         return null;
     }
 
     @Override
-    public IMount createDataMount( ItemStack stack, World world )
+    public IMount createDataMount( @Nonnull ItemStack stack, @Nonnull World world )
     {
         ServerComputer computer = createServerComputer( world, null, null, stack );
         if( computer != null )

src/main/java/dan200/computercraft/shared/pocket/recipes/PocketComputerUpgradeRecipe.java

@@ -16,6 +16,8 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.item.crafting.IRecipe;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class PocketComputerUpgradeRecipe implements IRecipe
 {
     public PocketComputerUpgradeRecipe()
@@ -35,13 +37,13 @@ public class PocketComputerUpgradeRecipe implements IRecipe
     }
 
     @Override
-    public boolean matches( InventoryCrafting inventory, World world )
+    public boolean matches( @Nonnull InventoryCrafting inventory, @Nonnull World world )
     {
         return (getCraftingResult( inventory ) != null);
     }
 
     @Override
-    public ItemStack getCraftingResult( InventoryCrafting inventory )
+    public ItemStack getCraftingResult( @Nonnull InventoryCrafting inventory )
     {
         // Scan the grid for a pocket computer
         ItemStack computer = null;
@@ -112,8 +114,9 @@ public class PocketComputerUpgradeRecipe implements IRecipe
         return PocketComputerItemFactory.create( computerID, label, family, upgrade );
     }
 
+    @Nonnull
     @Override
-    public ItemStack[] getRemainingItems( InventoryCrafting inventoryCrafting )
+    public ItemStack[] getRemainingItems( @Nonnull InventoryCrafting inventoryCrafting )
     {
         ItemStack[] results = new ItemStack[ inventoryCrafting.getSizeInventory() ];
         for (int i = 0; i < results.length; ++i)

src/main/java/dan200/computercraft/shared/turtle/apis/TurtleAPI.java

@@ -19,6 +19,7 @@ import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.ResourceLocation;
 
+import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -58,6 +59,7 @@ public class TurtleAPI implements ILuaAPI
     {
     }
        
+    @Nonnull
     @Override
     public String[] getMethodNames()
     {
@@ -181,7 +183,7 @@ public class TurtleAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( ILuaContext context, int method, Object[] args ) throws LuaException, InterruptedException
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
     {
         switch( method )
         {

src/main/java/dan200/computercraft/shared/turtle/blocks/BlockTurtle.java

@@ -27,6 +27,8 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
+import javax.annotation.Nonnull;
+
 public class BlockTurtle extends BlockComputerBase
 {
     // Statics
@@ -54,6 +56,7 @@ public class BlockTurtle extends BlockComputerBase
         );
     }
 
+    @Nonnull
     @Override
     public EnumBlockRenderType getRenderType( IBlockState state )
     {
@@ -72,12 +75,14 @@ public class BlockTurtle extends BlockComputerBase
         return false;
     }
 
+    @Nonnull
     @Override
     protected BlockStateContainer createBlockState()
     {
         return new BlockStateContainer(this, Properties.FACING );
     }
 
+    @Nonnull
     @Override
     public IBlockState getStateFromMeta( int meta )
     {
@@ -90,8 +95,9 @@ public class BlockTurtle extends BlockComputerBase
         return 0;
     }
 
+    @Nonnull
     @Override
-    public IBlockState getActualState( IBlockState state, IBlockAccess world, BlockPos pos )
+    public IBlockState getActualState( @Nonnull IBlockState state, IBlockAccess world, BlockPos pos )
     {
         return state.withProperty( Properties.FACING, getDirection( world, pos ) );
     }

src/main/java/dan200/computercraft/shared/turtle/blocks/TileTurtle.java

@@ -34,6 +34,7 @@ import net.minecraft.util.math.*;
 import net.minecraft.util.text.*;
 import net.minecraftforge.common.util.Constants;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 
 public class TileTurtle extends TileComputerBase
@@ -144,7 +145,7 @@ public class TileTurtle extends TileComputerBase
     }
 
     @Override
-    public void getDroppedItems( List<ItemStack> drops, boolean creative )
+    public void getDroppedItems( @Nonnull List<ItemStack> drops, boolean creative )
     {
         IComputer computer = getComputer();
         if( !creative || (computer != null && computer.getLabel() != null) )
@@ -243,6 +244,7 @@ public class TileTurtle extends TileComputerBase
         }
     }
 
+    @Nonnull
     @Override
     public AxisAlignedBB getBounds()
     {
@@ -293,7 +295,7 @@ public class TileTurtle extends TileComputerBase
     }
 
     @Override
-    public void onNeighbourTileEntityChange(BlockPos neighbour)
+    public void onNeighbourTileEntityChange( @Nonnull BlockPos neighbour)
     {
         if ( m_moveState == MoveState.NOT_MOVED )
         {
@@ -342,6 +344,7 @@ public class TileTurtle extends TileComputerBase
         m_brain.readFromNBT( nbttagcompound );
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound writeToNBT( NBTTagCompound nbttagcompound )
     {
@@ -539,6 +542,7 @@ public class TileTurtle extends TileComputerBase
         }
     }
 
+    @Nonnull
     @Override
     public String getName()
     {
@@ -569,6 +573,7 @@ public class TileTurtle extends TileComputerBase
         return false;
     }
 
+    @Nonnull
     @Override
     public ITextComponent getDisplayName()
     {
@@ -589,17 +594,17 @@ public class TileTurtle extends TileComputerBase
     }
 
     @Override
-    public void openInventory( EntityPlayer player )
+    public void openInventory( @Nonnull EntityPlayer player )
     {
     }
 
     @Override
-    public void closeInventory( EntityPlayer player )
+    public void closeInventory( @Nonnull EntityPlayer player )
     {
     }
 
     @Override
-    public boolean isItemValidForSlot( int slot, ItemStack stack )
+    public boolean isItemValidForSlot( int slot, @Nonnull ItemStack stack )
     {
         return true;
     }
@@ -625,7 +630,7 @@ public class TileTurtle extends TileComputerBase
     }
 
     @Override
-    public boolean isUseableByPlayer( EntityPlayer player )
+    public boolean isUseableByPlayer( @Nonnull EntityPlayer player )
     {
         return isUsable( player, false );
     }
@@ -666,14 +671,14 @@ public class TileTurtle extends TileComputerBase
     // Networking stuff
 
     @Override
-    public void writeDescription( NBTTagCompound nbttagcompound )
+    public void writeDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.writeDescription( nbttagcompound );
         m_brain.writeDescription( nbttagcompound );
     }
 
     @Override
-    public void readDescription( NBTTagCompound nbttagcompound )
+    public void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
         m_brain.readDescription( nbttagcompound );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleBrain.java

@@ -32,6 +32,7 @@ import net.minecraft.util.text.*;
 import net.minecraft.world.World;
 import net.minecraftforge.common.util.Constants;
 
+import javax.annotation.Nonnull;
 import java.lang.ref.WeakReference;
 import java.util.*;
 
@@ -473,12 +474,14 @@ public class TurtleBrain implements ITurtleAccess
         m_fuelLevel = nbttagcompound.getInteger( "fuelLevel" );
     }
 
+    @Nonnull
     @Override
     public World getWorld()
     {
         return m_owner.getWorld();
     }
 
+    @Nonnull
     @Override
     public BlockPos getPosition()
     {
@@ -486,7 +489,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public boolean teleportTo( World world, BlockPos pos )
+    public boolean teleportTo( @Nonnull World world, @Nonnull BlockPos pos )
     {
         if( world.isRemote || getWorld().isRemote )
         {
@@ -555,6 +558,7 @@ public class TurtleBrain implements ITurtleAccess
         return false;
     }
 
+    @Nonnull
     @Override
     public Vec3d getVisualPosition( float f )
     {
@@ -596,6 +600,7 @@ public class TurtleBrain implements ITurtleAccess
         return yaw;
     }
 
+    @Nonnull
     @Override
     public EnumFacing getDirection()
     {
@@ -603,7 +608,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public void setDirection( EnumFacing dir )
+    public void setDirection( @Nonnull EnumFacing dir )
     {
         if( dir.getAxis() == EnumFacing.Axis.Y )
         {
@@ -635,6 +640,7 @@ public class TurtleBrain implements ITurtleAccess
         }
     }
 
+    @Nonnull
     @Override
     public IInventory getInventory()
     {
@@ -711,8 +717,9 @@ public class TurtleBrain implements ITurtleAccess
         return m_commandsIssued;
     }
 
+    @Nonnull
     @Override
-    public Object[] executeCommand( ILuaContext context, ITurtleCommand command ) throws LuaException, InterruptedException
+    public Object[] executeCommand( @Nonnull ILuaContext context, @Nonnull ITurtleCommand command ) throws LuaException, InterruptedException
     {
         if( getWorld().isRemote )
         {
@@ -742,7 +749,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public void playAnimation( TurtleAnimation animation )
+    public void playAnimation( @Nonnull TurtleAnimation animation )
     {
         if( getWorld().isRemote )
         {
@@ -798,7 +805,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public ITurtleUpgrade getUpgrade( TurtleSide side )
+    public ITurtleUpgrade getUpgrade( @Nonnull TurtleSide side )
     {
         if( m_upgrades.containsKey( side ) )
         {
@@ -808,7 +815,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public void setUpgrade( TurtleSide side, ITurtleUpgrade upgrade )
+    public void setUpgrade( @Nonnull TurtleSide side, ITurtleUpgrade upgrade )
     {
         // Remove old upgrade
         if( m_upgrades.containsKey( side ) )
@@ -846,7 +853,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public IPeripheral getPeripheral( TurtleSide side )
+    public IPeripheral getPeripheral( @Nonnull TurtleSide side )
     {
         if( m_peripherals.containsKey( side ) )
         {
@@ -855,6 +862,7 @@ public class TurtleBrain implements ITurtleAccess
         return null;
     }
 
+    @Nonnull
     @Override
     public NBTTagCompound getUpgradeNBTData( TurtleSide side )
     {
@@ -866,7 +874,7 @@ public class TurtleBrain implements ITurtleAccess
     }
 
     @Override
-    public void updateUpgradeNBTData( TurtleSide side )
+    public void updateUpgradeNBTData( @Nonnull TurtleSide side )
     {
         m_owner.updateBlock();
     }

src/main/java/dan200/computercraft/shared/turtle/core/TurtleCheckRedstoneCommand.java

@@ -11,6 +11,8 @@ import dan200.computercraft.api.turtle.ITurtleCommand;
 import dan200.computercraft.api.turtle.TurtleCommandResult;
 import dan200.computercraft.core.apis.IAPIEnvironment;
 
+import javax.annotation.Nonnull;
+
 public class TurtleCheckRedstoneCommand implements ITurtleCommand
 {
     private final IAPIEnvironment m_environment;
@@ -22,8 +24,9 @@ public class TurtleCheckRedstoneCommand implements ITurtleCommand
         m_direction = direction;
     }
 
+    @Nonnull
     @Override
-    public TurtleCommandResult execute( ITurtleAccess turtle )
+    public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
     {
         // Do the checking
         int redstoneSide;

src/main/java/dan200/computercraft/shared/turtle/core/TurtleCompareCommand.java

@@ -19,6 +19,7 @@ import net.minecraft.util.EnumFacing;
 import net.minecraft.world.World;
 import net.minecraftforge.fml.relauncher.ReflectionHelper;
 
+import javax.annotation.Nonnull;
 import java.lang.reflect.Method;
 import java.util.Iterator;
 
@@ -31,8 +32,9 @@ public class TurtleCompareCommand implements ITurtleCommand
         m_direction = direction;
     }
 
+    @Nonnull
     @Override
-    public TurtleCommandResult execute( ITurtleAccess turtle )
+    public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
     {
         // Get world direction from direction
         EnumFacing direction = m_direction.toWorldDir( turtle );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleCompareToCommand.java

@@ -12,6 +12,8 @@ import dan200.computercraft.api.turtle.TurtleCommandResult;
 import dan200.computercraft.shared.util.InventoryUtil;
 import net.minecraft.item.ItemStack;
 
+import javax.annotation.Nonnull;
+
 public class TurtleCompareToCommand implements ITurtleCommand
 {
     private final int m_slot;
@@ -21,8 +23,9 @@ public class TurtleCompareToCommand implements ITurtleCommand
         m_slot = slot;
     }
 
+    @Nonnull
     @Override
-    public TurtleCommandResult execute( ITurtleAccess turtle )
+    public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
     {
         ItemStack selectedStack = turtle.getInventory().getStackInSlot( turtle.getSelectedSlot() );
         ItemStack stack = turtle.getInventory().getStackInSlot( m_slot );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleCraftCommand.java

@@ -16,6 +16,7 @@ import dan200.computercraft.shared.util.WorldUtil;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.math.BlockPos;
 
+import javax.annotation.Nonnull;
 import java.util.ArrayList;
 
 public class TurtleCraftCommand implements ITurtleCommand
@@ -27,8 +28,9 @@ public class TurtleCraftCommand implements ITurtleCommand
         m_limit = limit;
     }
 
+    @Nonnull
     @Override
-    public TurtleCommandResult execute( ITurtleAccess turtle )
+    public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
     {
         // Craft the item
         TurtleInventoryCrafting crafting = new TurtleInventoryCrafting( turtle );