设计要求：

设计一个计算器，用GUI画出来一个图形界面，有两个输入框，一个输出框，有4个加减乘除按钮，实现简单的加减乘除功能。

code：

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;public class cal extends Frame implements ActionListener
{private Button plus,minus,mul,div;private TextField Text1,Text2,Text3;private int a,b;public cal(){super("计算器小程序");plus=new Button("+");minus=new Button("-");mul=new Button("*");div=new Button("/");Text1=new TextField("输入第一个数",20);Text2=new TextField("输入第二个数",20);Text3=new TextField("结果",20);//Text1.setEditable(false); this.setSize(300,200);this.setBackground(Color.blue);this.setLocation(300,240);this.setLayout(new FlowLayout(FlowLayout.LEFT));this.add(Text1);this.add(Text2);this.add(Text3);this.add(plus); this.add(minus); this.add(mul);this.add(div);plus.addActionListener(this);minus.addActionListener(this);mul.addActionListener(this);div.addActionListener(this);this.addWindowListener(new Wadapt());this.setVisible(true); }public void actionPerformed(ActionEvent e){a = Integer.parseInt(Text1.getText());b = Integer.parseInt(Text2.getText());if(e.getSource()==plus){String s = String.valueOf(a+b);Text3.setText(s);}else if(e.getSource()==minus){String s = String.valueOf(a-b);Text3.setText(s);}else if(e.getSource()==mul){String s = String.valueOf(a*b);Text3.setText(s);}else if(e.getSource()==div){if (b==0) {Text3.setText("不合法的数据！");}else {String s = String.valueOf(a/b);Text3.setText(s);}}  }public static void main(String args[]){cal mycal=new cal();}
}
class Wadapt extends WindowAdapter
{public void windowClosing(WindowEvent evt){Frame frm=(Frame)evt.getSource();frm.setVisible(false);frm.dispose();System.exit(0);}
}