Calculator

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import javax.swing.*;

public class Calculator extends JFrame implements ActionListener{
	//声明组件
	JTextField t1, t2, t3;
	JButton add, sub, tim, div;
	JButton save;
	//属性，变量
	double result=0;
	
	Calculator(){
		init();
        this.setTitle("Calculator");
		this.setLayout(new FlowLayout());
		this.setSize(500, 500);
		this.setVisible(true);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	void init() {
		//新建组件
		t1=new JTextField(10);
		t2=new JTextField(10);
		t3=new JTextField(20);
		add=new JButton("+");
		sub=new JButton("-");
		tim=new JButton("*");
		div=new JButton("/");
		save=new JButton("save");
		
		//添加组件
		add(t1);
		add(t2);
		add(t3);
		add(add);
		add(sub);
		add(tim);
		add(div);
		add(save);
		
		//注册监听
		t1.addActionListener(this);
		t2.addActionListener(this);
		t3.addActionListener(this);
		sub.addActionListener(this);
		add.addActionListener(this);
		tim.addActionListener(this);
		div.addActionListener(this);
		save.addActionListener(this);
		//额外功能
		t3.setEditable(false);
	}
	
	@Override
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		String first=t1.getText();
		String second=t2.getText();
		double n1 =Double.parseDouble(first);
		double n2=Double.parseDouble(second);

		if(e.getSource().equals(add)) {
			result=n1+n2;
		}
		else if(e.getSource().equals(sub)) {
			result=n1-n2;
		}
		else if(e.getSource().equals(tim)) {
			result=n1*n2;
		}
		else if(e.getSource().equals(div)) {
			result=n1/n2;
		}
		else if(e.getSource().equals(save)) {
			try {
				File myObj=new File("result.txt");
				if(myObj.createNewFile()) 
					System.out.println("Successfully create the file "+myObj.getName());
				else
					System.out.println("The file already exists");
			}catch(IOException e1) {
				System.out.println("ERROR");
				e1.printStackTrace();
			}
			try {
				FileWriter w=new FileWriter("result.txt");
				w.write(result+"\n");
				System.out.println("Sucessfully wrote to the file");
				w.close();
			}catch(IOException e1) {
				System.out.println("ERROR");
				e1.printStackTrace();
			}
		}
		
		t3.setText(result+"\n");
		
	}
	
	public static void main(String args[]) {
		Calculator c=new Calculator();
	}
}

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class Calc extends JFrame implements ActionListener{
	
	JButton b1,b2,b3,b4;
	JTextField t1,t2,t3;

	Calc(){
		init();
		this.setSize(300, 300);
		this.setTitle("计算");
		this.setLayout(new FlowLayout());
		this.setVisible(true);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	
	void init() {
		b1=new JButton("加");
		b2=new JButton("减");
		b3=new JButton("乘");
		b4=new JButton("除");
		t1=new JTextField(10);
		t2=new JTextField(10);
		t3=new JTextField(20);

		add(b1);
		add(b2);
		add(b3);
		add(b4);
		add(t1);
		add(t2);
		add(t3);

		t1.addActionListener(this);
		t2.addActionListener(this);
		b1.addActionListener(this);
		b2.addActionListener(this);
		b3.addActionListener(this);
		b4.addActionListener(this);
		
		t3.setEditable(false);
	}
	
	@Override
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		
		double n1;
		double n2;
		double result=0;
		
		if(e.getSource().equals(b1)) {
			try {
				n1=Double.parseDouble(t1.getText());
				n2=Double.parseDouble(t2.getText());
				result=n1+n2;
				t3.setText(String.valueOf(result));
			}catch(NumberFormatException ee) {
				t3.setText("请输入数字");
			}
		}
		else if(e.getSource().equals(b2)) {
			try {
				n1=Double.parseDouble(t1.getText());
				n2=Double.parseDouble(t2.getText());
				result=n1-n2;
				t3.setText(String.valueOf(result));
			}catch(NumberFormatException ee) {
				t3.setText("请输入数字");
			}
		}
		else if(e.getSource().equals(b3)) {
			try {
				n1=Double.parseDouble(t1.getText());
				n2=Double.parseDouble(t2.getText());
				result=n1*n2;
				t3.setText(String.valueOf(result));
			}catch(NumberFormatException ee) {
				t3.setText("请输入数字");
			}
		}
		else if(e.getSource().equals(b4)) {
			try {
				n1=Double.parseDouble(t1.getText());
				n2=Double.parseDouble(t2.getText());
				result=n1*n2;
				t3.setText(String.valueOf(result));
			}catch(NumberFormatException ee) {
				t3.setText("请输入数字");
			}
		}
		
	}
	
	public static void main(String args[]) {
		Calc c=new Calc();
	}
}