Java程序－－编写一个具有图形界面的计算器程序

import java.awt.*;
import java.awt.event.*;
import java.io.*;

public class Test implements ActionListener
{
Frame f = new Frame("一步运算计算器");//创建窗架
TextField[] tf = new TextField[3];
Label La1 = new Label("+");
Button btn = new Button("=");
int[] a = new int[3]; //储存数据

public Test()
{
f.setLayout(new FlowLayout());
f.setSize(400,100);

f.addWindowListener
(
new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
}
); //窗口关闭事件

btn.addActionListener //输出加法运算结果
(
new ActionListener()
{
public void actionPerformed(ActionEvent e)
{