Change canvas to double buffered drawing

src/com/annimon/turrets/GameCanvas.java

@@ -1,7 +1,6 @@
 package com.annimon.turrets;
 
 import java.awt.Canvas;
-import java.awt.Color;
 import java.awt.Graphics;
 import java.awt.image.BufferedImage;
 
@@ -11,24 +10,56 @@ import java.awt.image.BufferedImage;
  */
 public class GameCanvas extends Canvas {
     
+    private final Graphics G;
+    private final BufferedImage buffer;
+    private final Terrain terrain;
     private BufferedImage background;
     
     public GameCanvas() {
         setSize(Constants.WIDTH, Constants.HEIGHT);
         setPreferredSize(Constants.SCREEN_DIMENSION);
         
+        buffer = new BufferedImage(Constants.WIDTH, Constants.HEIGHT, BufferedImage.TYPE_INT_RGB);
+        G = buffer.createGraphics();
+        
         initBackground();
+        terrain = new Terrain(Constants.WIDTH);
+        terrain.generate(System.currentTimeMillis());
+        
+        new DrawingThread().start();
     }
 
     @Override
     public void paint(Graphics g) {
-        g.drawImage(background, 0, 0, null);
+        G.drawImage(background, 0, 0, null);
+        terrain.draw(G);
+        g.drawImage(buffer, 0, 0, null);
     }
-
+    
+    @Override
+    public void update(Graphics g) {
+        paint(g);
+    }
+    
     private void initBackground() {
         background = new BufferedImage(Constants.WIDTH, Constants.HEIGHT, BufferedImage.TYPE_INT_RGB);
         Graphics g = background.createGraphics();
         new Background().draw(g);
         g.dispose();
     }
+    
+    private class DrawingThread extends Thread {
+
+        private boolean keepRunning = true;
+
+        @Override
+        public void run() {
+            while (keepRunning) {
+                try {
+                    Thread.sleep(100);
+                } catch (InterruptedException ex) {}
+                repaint();
+            }
+        }
+    }
 }