Flickering Problems - Java-Gaming.org

Hello, im trying to create a simple 2d game but have run into huge problems when i try to draw the graphics. Every fifth second or so my monitor is flickering badly wich is very annyoing. Here is the source, any help is very appriciated:

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import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.image.BufferStrategy;
import javax.swing.*;

public class Game extends JFrame implements Runnable {
   
   final int SCREEN_WIDTH = 320;
   final int SCREEN_HEIGHT = 240;
   final int BIT_DEPTH = 16;
    final int REFRESH_RATE = 60;
    final int FPS = 60;
    
    float y,x,dx,dy;
    Image img1;
    
    //private InputManager inputManager = new InputManager();
   
   public static void main(String[] args){
      new Game().init(false);
   }
   
   void init(boolean fullscreen){
      setTitle("test");
      GraphicsConfiguration gc = getGraphicsConfiguration();
      GraphicsDevice gd = gc.getDevice();
      
      if(fullscreen) {
         setUndecorated(true);
           gd.setFullScreenWindow(this);
           gd.setDisplayMode(new DisplayMode(SCREEN_WIDTH,SCREEN_HEIGHT,BIT_DEPTH, REFRESH_RATE));
        }
      
        else {
           setBounds(0,0,SCREEN_WIDTH,SCREEN_HEIGHT);
           setVisible(true);
        }
      
        //remove cursor
            Image cursorImage = Toolkit.getDefaultToolkit().getImage("sprites/transparent.gif");
         Cursor blankCursor = Toolkit.getDefaultToolkit().createCustomCursor(cursorImage, new Point( 0, 0), "" );
         setCursor( blankCursor );
         //
        
        setResizable(false);
        setIgnoreRepaint(true);

        //addKeyListener(inputManager);
        
        img1 = loadImage("test.png");
        x = 40; y = 50; dx = 1;

        Thread t = new Thread(this);
        t.start();
   }
   
   public Image loadImage(String filename){
      return new ImageIcon("images/"+filename).getImage();
   }
   
   public void run(){
        final int NANO_FRAME_LENGTH = 1000000000/FPS;
        long startTime = System.nanoTime();
        int frameCount = 0;

        while(true) {
           BufferStrategy bs = getBufferStrategy();
           Graphics2D g = (Graphics2D)bs.getDrawGraphics();
           
           if(x < 0 || x > 320)dx = -dx;
           x += dx;
           //misc rendering
           g.setColor(Color.BLUE);
           g.fillRect(0,0,SCREEN_WIDTH,SCREEN_HEIGHT);
           g.drawImage(img1,Math.round(x),Math.round(y),null);
           bs.show();
           frameCount++;
           // note:System.nanoTime in 1.5+
           while((System.nanoTime()-startTime)/NANO_FRAME_LENGTH <frameCount) {
              Thread.yield();
           }
        }
   }
}