java - Graphics are flickering when I draw with double buffering -

i'm building simple 2d java game , having flickering issues though draw graphics using double buffering technique.

i've got started , have simple game loop far. think should work fine anyway? without flickering.. here's how it:

@override public void run() {     while (running) {         currentstate.update();         preparegameimage();         currentstate.render(gameimage.getgraphics());         repaint();         try {             thread.sleep(14);         } catch (interruptedexception e) {             e.printstacktrace();         }     }      system.exit(0); }  @override protected void paintcomponent(graphics g) {     super.paintcomponent(g);     if (gameimage == null) {         return;     }     g.drawimage(gameimage, 0, 0, null); }  private void preparegameimage() {     if (gameimage == null) {         gameimage = createimage(gamewidth, gameheight);     }      graphics g = gameimage.getgraphics();     g.clearrect(0, 0, gamewidth, gameheight); } 

you can see how mean in this video

i'm looking tips lead me whats causing glitch. doing double buffering wrong?

any appreciated!

thanks