问题１

来源：互联网发布：知乎化妆品网站编辑：程序博客网时间：2024/04/27 20:36

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class HelloJava3
extends JComponent
implements MouseMotionListener,ActionListener{
   int mx=145,my=79; // initial x,y 的坐标
   String theMe;// message
   JButton theButton;

   //create someColors arry[]
   int colorIndex;
   static Color[] someColors={
    Color.black,Color.blue,Color.cyan,Color.darkGray,Color.darkGray,Color.green,
    Color.orange
   };

   public HelloJava3(String message){
    theButton=new JButton("Change Color");
    theMe =message;
    setLayout(new FlowLayout());
    add(theButton);
    theButton.addActionListener(this);
    addMouseMotionListener(this);

}

   public void paintComponent(Graphics g){
   g.drawString("Happy new year",125,100);
   g.drawString("fill",125,95);
   g.drawString(theMe,mx,my);

}

public void mouseDragged(MouseEvent e){
   mx=e.getX();
   my=e.getY();
   repaint();

}

public void mouseMoved(MouseEvent e){
//这里没有代码表示可以忽略这个方法
}

public void actionPerformed(MouseEvent e){
if (e.getSource()==theButton)
changeColor();

}
// 第一次用sychronized

synchronized private void changeColor(){
   //递增索引
   if (++colorIndex==someColors.length)
    colorIndex=0;
    setForeground(currentColor());
    repaint();

}

synchronized private Color currentColor(){
return someColors[colorIndex];

}
public static void main (String[] args) {
         JFrame f=new JFrame("HelloJava3");
         f.addWindowListener(new WindowAdapter(){
          public void windowClosing(WindowEvent we){
           System.exit(0);
          }
         });
         f.setSize(250,250);
         f.getContentPane().add(new HelloJava3("Hello !Java"));
         f.setLocation(500,500);
          f.setVisible(true);

}

/*E:/Java/jkk/HelloJava3.java:5: HelloJava3 不是抽象的，并且未覆盖 java.awt.event.ActionListener 中的抽象方法 actionPerformed(java.awt.event.ActionEvent)
public class HelloJava3
*/

//我写的程序为什么编译时会出现这个问题？求助！！！！