java - How to fix bad Double-Buffering -

i tried following double buffering tutorial, , don't know did wrong. works before before did tutorial, there still , occasional flicker here , there. have 2 files game , gameloop

game:

import java.awt.graphics; public class game extends gameloop {     public void init()     {         setsize(854,480);         thread th = new thread(this);         th.start();         offscreen = createimage(854,480);         d = offscreen.getgraphics();     }     public void paint(graphics g)     {         d.clearrect(0, 0, 854, 480);         d.drawimage(disk, x, y, this);         g.drawimage(offscreen , 0, 0, this);     }     public void update(graphics gfx)     {         paint(gfx);     } } 

gameloop

import java.applet.applet; import java.awt.graphics; import java.awt.image; import java.awt.mouseinfo; import java.awt.point; import java.awt.pointerinfo; import java.awt.event.keyevent; import java.awt.event.keylistener; import java.awt.event.mouseevent; import java.awt.event.mouselistener; import java.awt.event.mousemotionlistener; import java.awt.image.bufferedimage; import java.io.file; import java.io.ioexception;  import javax.imageio.imageio;  public class gameloop extends applet implements runnable, mouselistener, mousemotionlistener  {     public int x, y, counter, mousex, mousey;     public image offscreen;     public graphics d;     public boolean up, down, left, right, pressed;     public bufferedimage disk1, disk2, disk3, disk4, disk;     public int ballspeedx = -6;     public int ballspeedy = -3;      public void run()      {         x = 400;         y = 200;         try {             disk1 = imageio.read(new file("disk1.png"));             disk2 = imageio.read(new file("disk2.png"));             disk3 = imageio.read(new file("disk3.png"));             disk4 = imageio.read(new file("disk4.png"));         } catch (ioexception e1) {             e1.printstacktrace();         }         while(true)         {             if(x >= (854 - 150))             {                     ballspeedx = ballspeedx * -1;             }             if(y >= (480 - 140))             {                     ballspeedy = ballspeedy * -1;             }             if(y < (0 - 10))             {                     ballspeedy = ballspeedy * -1;             }             if(x < (0- 10))             {                     ballspeedx = ballspeedx * -1;             }              x = x + ballspeedx;             y = y + ballspeedy;              counter ++;             if(counter >= 4)                 counter = 0;              if(counter == 0)                 disk = disk1;             if(counter == 1)                 disk = disk2;             if(counter == 2)                 disk = disk3;             if(counter == 3)                 disk = disk4;              system.out.println(counter);              repaint();              try {                 thread.sleep(30);             } catch (interruptedexception e) {                 e.printstacktrace();             }         }     }        public void mouseclicked(mouseevent e) {}     public void mouseentered(mouseevent e) {}     public void mouseexited(mouseevent e) {}     public void mousemoved(mouseevent m) {}      public void mousepressed(mouseevent m)      {      }      public void mousereleased(mouseevent m)      {         pressed = false;     }      public void mousedragged(mouseevent e) {         pointerinfo = mouseinfo.getpointerinfo();         point b  = a.getlocation();         mousex = (int)b.getx();         mousey = (int)b.gety();         ballspeedx = mousex;         ballspeedy = mousey;     } } 

public void update(graphics gfx) {     paint(gfx); } 

should lower case, you're trying override update(graphics g) method in applet.

so should be

@override public void update(graphics gfx) {     paint(gfx); } 

as changing background, background big rectangle covers screen , makes color. in paint, you're doing clearrect, clears screen. instead switch fillrect after setting color.

it might like

public void paint(graphics g) {     //setcolor whatever want     //fillrect cover screen } 

when you're doing though, 1 thing have remember not confuse 2 graphics objects. concept, double buffering works drawing memory first (drawing on offscreen image) , screen. want draw onto offscreen image, faster (and lose flicker).

so make sure you're doing imagegraphicsobject.setcolor not screengraphicsobject.setcolor or imagegraphicsobject.fillrectnotscreengraphicsobject.fillrect`. otherwise you're no longer double-buffering.