My repaint( ) just re-paints but doesn't clear the back

Question

Hi, i am using repaint( ) with the timer method to randomly draw 100 randomly colored lines.But every time the timer calls actionperformed which contains repaint( ), the application just paints the new 100 lines on top of the old ones, not cleaning the first painting. Maybe this is the way to repaint continuesly, but isn't repaint( ) supposed to clear the back. Here is my code, thanks for helping!
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class RandomLines extends JFrame
implements ActionListener {
private int x1,y1,x2,y2;
private int r,gr,b;
Timer timer;
public RandomLines()
super("Drawing Random Lines");
timer=new Timer(10000, this);
timer.start();
setSize(400,400);
show();
public void paint(Graphics g)
for(int i=1;i<=100;i++)
x1=1+(int)(Math.random()*399);
y1=1+(int)(Math.random()*399);
x2=1+(int)(Math.random()*399);
y2=1+(int)(Math.random()*399);
r=1+(int)(Math.random()*255);
gr=1+(int)(Math.random()*255);
b=1+(int)(Math.random()*255);
g.setColor(new Color(r,gr,b));
g.drawLine(x1,y1,x2,y2);
public void actionPerformed(ActionEvent e)
repaint();
public static void main(String args[])
RandomLines app=new RandomLines();
app.addWindowListener(
new WindowAdapter() {
public void windowClosing(WindowEvent e)
System.exit(0);
}

Answer 1

I reckon this might be part of it:
Container update(Graphics g):
Updates the container. This forwards the update to any lightweight components that are children of this container. If this method is reimplemented, super.update(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, update() will not be forwarded to that child.
Component update(Graphics g):
Updates this component.
The AWT calls the update method in response to a call to repaintupdate or paint. You can assume that the background is not cleared.
The updatemethod of Component does the following:
Clears this component by filling it with the background color.
Sets the color of the graphics context to be the foreground color of this component.
Calls this component's paint method to completely redraw this component.
The apparently contradictory statements in the definition for Component are slightly puzzling - maybe they mean that "You can assume that the background has yet to be cleared"? This would also seem to imply that a Panel, being a container, does not clear its background, but that a Canvas does. I can't remember if this is the case. Anyone care to verify?--
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