用JAVA编写一个简单的屏幕变色程序，当用户单击“变色”按钮时，窗口颜色就自动地变成另外一种颜色。

import java.awt.*

import java.awt.event.*

import java.applet.*

public class ColorChange extends Applet implements MouseListener

{Button btn=new Button("变色")

public void init()

{btn.addMouseListener(this)

this.add(btn)}//将鼠标事件注册

public void mouseEntered(MouseEvent e){

}

public void mouseExited(MouseEvent e){

setBackground(Color.white)}

public void mousePressed(MouseEvent e)

{}

public void mouseReleased(MouseEvent e)

{}

public void mouseClicked(MouseEvent e){

setBackground(Color.green)

repaint()

}

}

package com.test5

import java.applet.*

import java.awt.Color

import java.awt.GridLayout

import java.awt.event.*

import javax.swing.*

public class ChangeColor extends Applet implements Runnable{

static JButton button1, button2, button3, button4

public void init() {

button1 = new JButton()

button2 = new JButton()

button3 = new JButton()

button4 = new JButton()

JFrame change = new JFrame("变色")

setLayout(new GridLayout(2, 2))

add(button4)

add(button1)

add(button2)

add(button3)

setSize(300, 300)

ActionListener command = new ActionListener() {

public void actionPerformed(ActionEvent event) {

//run()//直接调用run（）方法看不到任何效果，因为程序执行时间太快了，如果采用线程睡眠（即暂停1S），就OK

Thread t1=new Thread(new ChangeColor())

t1.start()

}

}

button1.addActionListener(command)

button2.addActionListener(command)

button3.addActionListener(command)

button4.addActionListener(command)

//初始化即起动线程，然后单击按钮再启动线程，都能看到效果。

Thread t=new Thread(this)

t.start()

}

public void run() {

Color b[] = { Color.cyan, Color.yellow, Color.red, Color.blue,

Color.green, Color.black, Color.DARK_GRAY, Color.MAGENTA,

Color.PINK, Color.darkGray }

JButton a[] = { button1, button2, button3, button4 }

try {

for (int i = 0i <4i++){

a[i].setBackground(b[(int) (Math.random() * 10)])

Thread.sleep(1000)

}

} catch (Exception e) {

// TODO 自动生成 catch 块

e.printStackTrace()

}

}

}

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