在以下程序中，鼠标单击小应用程序的某一点，则会在该点显示一个图标，如果双击，则会清除该图标。且在浏览器的状态栏上会显示鼠标单击位置的坐标。运行结果如下图所示。请改正程序中的错误(有下划线的语句)，使程序能输出正确的结果。
注意：不改动程序的结构，不是增行或删行。
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Example3_1 extends Applet
int xPoint, yPoint;
int sum;
Image displayIm;
public void init()
displayIm = getImage("ms.jpg");
addMouseListener(new SClickMouse()) ;
sum = 2;
public void paint(Graphics g)
if(sum == 1)
g.drawImage(displayIm, xPoint, yPoint, this);
else
g.fillRect(xPoint, yPoint, 60, 60);
public class SClickMouse implements MouseListener
public void mouseClicked(MouseEvent mouse)
sum = mouse.getClickCount();
xPoint = mouse.getX();
yPoint = mouse.getY();
paint();
public void mouseEntered(MouseEvent mouse)
public void mouseExited(MouseEvent mouse)
public void mousePressed(MouseEvent mouse)
xPoint = mouse.getX();
yPoint = mouse.getY();
showStatus("x="+xPoint+",y-"+yPoint);
public void mouseReleased(MouseEvent mouse)
Exampie3_1.html:
＜html＞
＜head＞＜title＞Example3_1＜/title＞＜/head＞
＜body＞
＜applet code="Example3_1.class" width="400" height="500"＞
＜/applet＞
＜/body＞
＜/html＞
