为什么我drawString的时候，总是在原来的地方继续draw，而没有擦去原来的string？

Question

while(i < 3)
{ 
                           //在这里画一个矩形当背景。 g.drawString("number" + i, 50, 50);
i++;
}

Answer 1

import java.awt.*;
import javax.swing.*;
import java.util.Timer;
import java.awt.event.*;
public class OKDraw extends JFrame implements ActionListener
{
        int i;
        javax.swing.Timer timer=new javax.swing.Timer(1000,this);//±í&Ecirc;&frac34;1000&ordm;&Aacute;&Atilde;&euml;&Ograve;&raquo;&Ouml;&iexcl;&para;&macr;&raquo;&shy;
        
        public OKDraw()
        {
                timer.start();
                setSize(300, 400);
        }
        
        public void paint(Graphics g)
        {
                super.paint(g);//&Otilde;&acirc;&frac34;&auml;&raquo;°·&Ccedil;&sup3;&pound;&Ouml;&Oslash;&Ograve;&ordf;&pound;&not;&sup2;&raquo;&Ograve;&ordf;&Euml;ü&micro;&Auml;&raquo;°&raquo;&sup1;&Ecirc;&Ccedil;&raquo;á&Oacute;&ETH;&Ouml;&Oslash;&micro;&thorn;&iexcl;&pound;
                //g.clearRect(50, 50, 300, 300);
                g.drawString("number: " + i, 50, 50);
        }
        
        public void actionPerformed(ActionEvent e)
        {
                if(i<10)//i&micro;&Auml;&Ouml;&micro;&Eacute;è&para;¨&Icirc;&ordf;&micro;&frac12;10&Icirc;&ordf;&Ouml;&sup1;
                {
                    i++;
                    repaint();
                }
        }
        
        public static void main(String[] args)
        {
                OKDraw md = new OKDraw();
                md.show();      
        }
}