Java语言程序设计课程实验题目 第四次实验

1. 在IDE中输入以下代码，观察运行结果，并说明该段程序的作用。

import java.awt.event.*;

import javax.swing.*;

 

public class ButtonExample extends JPanel {

         static JFrame myFrame;

       JLabel label;    

         public ButtonExample(){

             label = new JLabel ("Hello World!");

             JButton hello = new JButton("Hello");         

             // set shortcut key

             hello.setMnemonic('h');

             //Set the ToolTip for the hello button

             hello.setToolTipText("Press Alt+H to test shortcut key");

             hello.addActionListener(new ActionListener(){

                    public void actionPerformed(ActionEvent ae){

                             System.out.println("Hello World!");

                             label.setText("Hello World!");

                    }

           });

             JButton bye = new JButton("Bye");

             bye.setMnemonic('b');

             //Set the ToolTip for the bye button

            bye.setToolTipText("Press Alt+B to test shortcut key");

             bye.addActionListener(new ActionListener(){

                    public void actionPerformed(ActionEvent ae){

                             System.out.println("By