Mine

import java.awt.Toolkit;
import java.awt.Graphics;
import javax.swing.JPanel;
import java.awt.Image;

// handles the thread/update/render/paint

public abstract class GamePanel extends JPanel implements Runnable {
  // fps
  protected FPSCounter fpsCounter;

  // double buffer
  protected Graphics dbg;           // graphics used for gameRender()
  private Image dbImage = null;     // image used in paintScreen()

  // thread
  private Thread thread;
  private boolean running = false;

  // child methods
  public abstract void gameUpdate();
  public abstract void gameRender();
  public abstract void onExit();

  // hardcoded methods
  private void gamePreRender() {
    if (dbImage == null) {
      dbImage = createImage(this.getWidth(), this.getHeight());
      if (dbImage == null) {
        System.out.println("Error creating Image Buffer");
        return;
      } else {
        dbg = dbImage.getGraphics();
      }
    }
  }
  private void paintScreen() {
    Graphics g;
    try {
      g = this.getGraphics();
      if (g != null && dbImage != null) {
        g.drawImage(dbImage, 0, 0, null);
      }
      Toolkit.getDefaultToolkit().sync();
      g.dispose();
    }
    catch (Exception e) {
      System.out.println(e);
    }
  }

  protected void startThread(double desiredFPS,int count) {
    fpsCounter = new FPSCounter(desiredFPS,count);
    running = true;
    thread = new Thread(this);
    thread.start();
  }

  protected void stopThread() {
    running = false;
  }

  protected boolean getRunning() {
    return running;
  }

  // should not be overridden by child
  public void run() {
    while (running) {
      fpsCounter.startFrame();
      gameUpdate();
      gamePreRender();
      gameRender();
      paintScreen();
      fpsCounter.endFrame();
    }
    onExit();
  }
}