Java Program for Double Buffering

/*<applet code=DoubleBuffer width=250 height=250>
</applet>*/
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class DoubleBuffer extends Applet
{
int gap=3;
int mx,my;
boolean flicker=true;
Image buffer=null;
int w,h;
public void init()
{
Dimension d=getSize();
w=d.width;
h=d.height;
buffer=createImage(w,h);
addMouseMotionListener(new MouseMotionAdapter()
{
public void mouseDragged(MouseEvent me)
{
mx=me.getX();
my=me.getY();
flicker=false;
repaint();
}
public void mouseMoved(MouseEvent me)
{
mx=me.getX();
my=me.getY();
flicker=true;
repaint();
}
});
}
public void paint(Graphics g)
{
Graphics screengc=null;
if(!flicker)
{
screengc=g;
g=buffer.getGraphics();
}
g.setColor(Color.blue);
g.fillRect(0,0,w,h);
g.setColor(Color.red);
for(int i=0;i<w;i+=gap)
g.drawLine(i,0,w-i,h);
for(int i=0;i<h;i+=gap)
g.drawLine(i,0,w,h-i);
g.setColor(Color.black);
g.drawString("Press mouse button to double buffer",10,h/2);
g.setColor(Color.yellow);
g.fillOval(mx-gap,my-gap,gap*2+1,gap*2+1);
if(!flicker)
{
screengc.drawImage(buffer,0,0,null);
}
}
public void update(Graphics g)
{
paint(g);
}
}
OutPut: