PaintComponent(Graphics g) problem

Question

hi, guys:
Can someone tell me why my code is not work in paintComponent(Graphics g)
below are my code:
protected void paintComponent(Graphics g)
     g.drawLine(0, 0, 100, 100); //this line work
this.getGraphics().drawLine(0,0,100,100); //this is not work
I know I should use auto passed "Graphics g", however, I don't understand why this.getGraphics() can't do the same work. It should return the same Graphics object which I expected.
Thanks for help.

Answer 1

I just posted my code below (Applet), hope helpful.
package mypackage;
import java.applet.Applet;
import java.awt.*;
import javax.swing.*;
class CatchTheCreaturePanel extends JPanel
     private Creature[] creature;
     public CatchTheCreaturePanel()
          this.setPreferredSize(new Dimension(400,300));          
     public void paintComponent(Graphics g)
          g.drawLine(50, 70, 100, 100); //work
          this.getGraphics().drawLine(0, 0, 100, 100); //not work
public class Jmyass extends JApplet {
     private CatchTheCreaturePanel the_panel;
     public Jmyass() {
          super();
     public void init() {
          the_panel=new CatchTheCreaturePanel();
     public void start() {
          this.getContentPane().add(the_panel);          
}