Example on how to allow Space Invader Test Application to work as an applet with minimal code change.

src/java/org/lwjgl/examples/spaceinvaders/Game.java

@@ -167,6 +167,9 @@ public class Game {
 
   /** Mouse movement on x axis */
 	private int	mouseX;
+	
+	/** Is this an application or applet */
+	private static boolean isApplication = false;
 
 	/**
 	 * Construct our game and set it running.
@@ -210,13 +213,15 @@ public class Game {
 	public void initialize() {
 		// initialize the window beforehand
 		try {
-      setDisplayMode();
-      Display.setTitle(WINDOW_TITLE);
-      Display.setFullscreen(fullscreen);
-      Display.create();
-      
+			setDisplayMode();
+			Display.setTitle(WINDOW_TITLE);
+			Display.setFullscreen(fullscreen);
+			Display.create();
+	      
 			// grab the mouse, dont want that hideous cursor when we're playing!
-			Mouse.setGrabbed(true);
+			if (isApplication) {	
+				Mouse.setGrabbed(true);
+			}
 
 			// enable textures since we're going to use these for our sprites
 			GL11.glEnable(GL11.GL_TEXTURE_2D);
@@ -426,6 +431,10 @@ public class Game {
 			// update window contents
 			Display.update();
 		}
+		
+		// clean up
+		soundManager.destroy();
+		Display.destroy();
 	}
 
 	/**
@@ -542,7 +551,7 @@ public class Game {
 		}
 
 		// if escape has been pressed, stop the game
-		if (Display.isCloseRequested() || Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) {
+		if ((Display.isCloseRequested() || Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) && isApplication) {
 			Game.gameRunning = false;
 		}
 	}
@@ -579,6 +588,7 @@ public class Game {
 	 * @param argv The arguments that are passed into our game
 	 */
 	public static void main(String argv[]) {
+		isApplication = true;
 		System.out.println("Use -fullscreen for fullscreen mode");
 		new Game((argv.length > 0 && argv[0].equalsIgnoreCase("-fullscreen"))).execute();
 		System.exit(0);
@@ -587,10 +597,8 @@ public class Game {
 	/**
 	 * 
 	 */
-	private void execute() {
+	public void execute() {
 		gameLoop();
-		soundManager.destroy();
-		Display.destroy();
 	}
 
 	/**

src/java/org/lwjgl/examples/spaceinvaders/GameApplet.java

@@ -0,0 +1,104 @@
+package org.lwjgl.examples.spaceinvaders;
+
+
+import java.applet.Applet;
+import java.awt.BorderLayout;
+import java.awt.Canvas;
+import org.lwjgl.LWJGLException;
+import org.lwjgl.opengl.Display;
+
+public class GameApplet extends Applet {
+	
+	/** The Canvas where the LWJGL Display is added */
+	Canvas display_parent;
+	
+	/** Thread which runs the main game loop */
+	Thread gameThread;
+	
+	/** The Game instance */
+	Game game;
+	
+	/**
+	 * Once the Canvas is created its add notify method will call this method to 
+	 * start the LWJGL Display and game loop in another thread.
+	 */
+	public void startLWJGL() {
+		gameThread = new Thread() {
+			public void run() {
+				
+				try {
+					Display.setParent(display_parent);
+					
+				} catch (LWJGLException e) {
+					e.printStackTrace();
+				}
+				// start game
+				game = new Game(false);
+				game.execute();
+			}
+		};
+		gameThread.start();
+	}
+	
+	
+	/**
+	 * Tell game loop to stop running, after which the LWJGL Display will be destoryed.
+	 * The main thread will wait for the Display.destroy() to complete
+	 */
+	private void stopLWJGL() {
+		Game.gameRunning = false;
+		try {
+			gameThread.join();
+		} catch (InterruptedException e) {
+			e.printStackTrace();
+		}
+	}
+
+	public void start() {
+		
+	}
+
+	public void stop() {
+		
+	}
+	
+	/**
+	 * Applet Destroy method will remove the canvas, before canvas is destroyed it will notify 
+	 * stopLWJGL() to stop main game loop and to destroy the Display
+	 */
+	public void destroy() {
+		remove(display_parent);
+		super.destroy();
+		System.out.println("Clear up");
+	}
+	
+	/**
+	 * initialise applet by adding a canvas to it, this canvas will start the LWJGL Display and game loop
+	 * in another thread. It will also stop the game loop and destroy the display on canvas removal when 
+	 * applet is destroyed.
+	 */
+	public void init() {
+		setLayout(new BorderLayout());
+		try {
+			display_parent = new Canvas() {
+				public final void addNotify() {
+					super.addNotify();
+					startLWJGL();
+				}
+				public final void removeNotify() {
+					stopLWJGL();
+					super.removeNotify();
+				}
+			};
+			display_parent.setSize(getWidth(),getHeight());
+			add(display_parent);
+			display_parent.setFocusable(true);
+			display_parent.requestFocus();
+			display_parent.setIgnoreRepaint(true);
+			setVisible(true);
+		} catch (Exception e) {
+			System.err.println(e);
+			throw new RuntimeException("Unable to create display");
+		}
+	}
+}