按钮事件处理程序

代码如下所示：

import java.awt.*;import java.awt.event.*;import java.applet.*;public class ButtonDemo extends Applet implements ActionListener{String msg="";//定义按钮"是"、"否"、"取消"public void init(){Button yes=new Button("是");Button no= new Button("否");Button maybe=new Button("取消");add(yes);add(no);add(maybe);yes.addActionListener(this);no.addActionListener(this);maybe.addActionListener(this);}public void actionPerformed(ActionEvent e){String str=e.getActionCommand();if(str=="是"){msg="您单击了按钮'是'。";}else if(str=="否"){msg="您单击了按钮'否'。";}else {msg="您单击了按钮'取消'。";}repaint();}public void paint(Graphics g){g.drawString(msg,6,100);}}

运行结果：