JFrame先关类写的一个计算器代码

package com.yiyun.util;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.text.DecimalFormat;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class Calculator {
    //计算器面板
	private JFrame f = new JFrame("Calculator");
	//输入面扳
	private JPanel inputPanel = new JPanel();
	//加减乘除面板
	private JPanel operationPanel = new JPanel();
	//数字面板
	private JPanel buttonsPanel = new JPanel();
	
	//输入数据文本框
	private JTextField input = new JTextField(20);
	
	//退格键
	private JButton backspace = new JButton("BackSpace");
	//清空
	private JButton CE = new JButton("CE  ");
	//删除
	private JButton C = new JButton("C  ");
	
	//四则运算符号键
	private JButton add = new JButton("+");
	private JButton sub = new JButton("-");
	private JButton mul = new JButton("*");
	private JButton div = new JButton("/");
	
	//小数点
	private JButton decimal = new JButton(".");
	//等号
	private JButton equal = new JButton("=");
	
	//数字键
	private JButton zero = new JButton("0");
	private JButton one = new JButton("1");
	private JButton two = new JButton("2");
	private JButton three = new JButton("3");
	private JButton four = new JButton("4");
	private JButton five = new JButton("5");
	private JButton six = new JButton("6");
	private JButton seven = new JButton("7");
	private JButton eight = new JButton("8");
	private JButton nine = new JButton("9");
	
	private String num1 = "";//保存第一个运算数字
	private String operator = "";//保存运算符号
	
	public static void main(String[] args) {
		new Calculator();//new计算器实例
	}
	
	public Calculator(){
	     //添加组件，布局
		inputPanel.add(input);
		f.add(inputPanel, BorderLayout.NORTH);
		
		operationPanel.add(backspace);
		operationPanel.add(CE);
		operationPanel.add(C);
		f.add(operationPanel, BorderLayout.CENTER);
		
		buttonsPanel.add(add);
		buttonsPanel.add(sub);
		buttonsPanel.add(mul);
		buttonsPanel.add(div);
		buttonsPanel.add(one);
		buttonsPanel.add(two);
		buttonsPanel.add(three);
		buttonsPanel.add(zero);
		buttonsPanel.add(four);
		buttonsPanel.add(five);
		buttonsPanel.add(six);
		buttonsPanel.add(decimal);
		buttonsPanel.add(seven);
		buttonsPanel.add(eight);
		buttonsPanel.add(nine);
		buttonsPanel.add(equal);
		buttonsPanel.setLayout(new GridLayout(4, 4));
		f.add(buttonsPanel, BorderLayout.SOUTH);
		
		//注册各个组件监听事件
		backspace.addMouseListener(new OperationMouseListener());
		CE.addMouseListener(new OperationMouseListener());
		C.addMouseListener(new OperationMouseListener());
		decimal.addMouseListener(new OperationMouseListener());
		equal.addMouseListener(new OperationMouseListener());
		
		//注册四则运算监听
		add.addMouseListener(new CalcMouseListener());
		sub.addMouseListener(new CalcMouseListener());
		mul.addMouseListener(new CalcMouseListener());
		div.addMouseListener(new CalcMouseListener());
		
		//注册数字监听事件
		zero.addMouseListener(new NumberMouseListener());
		one.addMouseListener(new NumberMouseListener());
		two.addMouseListener(new NumberMouseListener());
		three.addMouseListener(new NumberMouseListener());
		four.addMouseListener(new NumberMouseListener());
		five.addMouseListener(new NumberMouseListener());
		six.addMouseListener(new NumberMouseListener());
		seven.addMouseListener(new NumberMouseListener());
		eight.addMouseListener(new NumberMouseListener());
		nine.addMouseListener(new NumberMouseListener());
		
		f.setVisible(true);
		f.pack();
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	
	private class NumberMouseListener implements MouseListener{
		public void mouseClicked(MouseEvent e) {
			if(input.getText().trim().equals("0")){//如果文本框已经是0，结果还是0
				input.setText(((JButton)e.getSource()).getText().trim());
			}else{//否则的话，把0添加到后面，譬如文本框是1，结果就为10
				input.setText(input.getText().concat(((JButton)e.getSource()).getText().trim()));
			}
		}
		public void mouseEntered(MouseEvent e) {}
		public void mouseExited(MouseEvent e) {}
		public void mousePressed(MouseEvent e) {}
		public void mouseReleased(MouseEvent e) {}	
	}
	
	private class CalcMouseListener implements MouseListener{
		//如果输入的是运算符号，保存第一个结果和运算符号
		public void mouseClicked(MouseEvent e) {
			num1 = input.getText().trim();input.setText("");
			operator = ((JButton)e.getSource()).getText().trim();
		}
		public void mouseEntered(MouseEvent e) {}
		public void mouseExited(MouseEvent e) {}
		public void mousePressed(MouseEvent e) {}
		public void mouseReleased(MouseEvent e) {}	
	}
	
	private class OperationMouseListener implements MouseListener{
		public void mouseClicked(MouseEvent e) {
			if(e.getSource() == backspace){//退格键，删除一个直到没有字符删除
				String inputText = input.getText();
				if(inputText.length() > 0){
					input.setText(inputText.substring(0, inputText.length() - 1));
				}
			}else if(e.getSource() == C){
				input.setText("0");//C，清空所有运算数字和符号
				num1 = "";
			}else if(e.getSource() == CE){
				input.setText("0");//CE-->将文本框置为0
			}else if(e.getSource() == decimal){
				String text = input.getText().trim();
				//如果按了小数点，如果文本框已经有小数点，不做任何操作，否则在结果后面加上小数点
				if(text.indexOf(".") == -1){
					input.setText(text.concat("."));
				}
			}else if(e.getSource() == equal){
				//如果是等号
				if(!operator.trim().equals("")){
					if(!input.getText().trim().equals("")){
						double result = 0D;
						if(operator.equals("+")){//执行加法运算
							result = Double.parseDouble(num1) + Double.parseDouble(input.getText().trim());
						}else if(operator.equals("-")){//减法运算
							result = Double.parseDouble(num1) - Double.parseDouble(input.getText().trim());
						}else if(operator.equals("*")){//乘法运算
							result = Double.parseDouble(num1) * Double.parseDouble(input.getText().trim());
						}else if(operator.equals("/")){//除法运算
							result = Double.parseDouble(num1) / Double.parseDouble(input.getText().trim());
						}
						 
						 //格式化最终结果，保留两位小数点
						input.setText(new DecimalFormat("0.00").format(result));
					}
				}
				
			}
			
		}
		public void mouseEntered(MouseEvent e) {}
		public void mouseExited(MouseEvent e) {}
		public void mousePressed(MouseEvent e) {}
		public void mouseReleased(MouseEvent e) {}	
	}
	
}