java实现简单计算器

java实现简单计算器

功能：简单计算器：两数运算，平方，加负号,实现了复制粘贴功能
 * 参考资料：《Java编程思想》、JDK1.6、 CSDN博客：http://blog.csdn.net/baidu_38132719/article/details/69221053?locationNum=4&fps=1
 * 2017.5.4于宁夏大学

下面是源代码，由于初学Java，许多东西知之甚少，因此代码的质量应该不高，有很多可以改进的地方；以后随着学习的进行我会继续修改的，希望大家提出意见和批评，谢谢

下面是源代码

import java.awt.*; import java.awt.event.*;import java.text.DecimalFormat;import javax.swing.*;public class Calculator implements ActionListener{private static JTextArea text_01, text_02;// 一个显示数据，一个显示“关于计算器”private static JButton bt[] = new JButton[20];// 20个按钮private static double result_01, tempret;// 一个存运算符前面的数字，一个存后面的private static int n = -1, temp;// n是运算符按下标志private static String s, stemp;// temp复制粘贴功能用 private static JMenu oprt, help, edit;// 三个菜单组件private static JMenuItem copy, paste, cut, about, exit;// 5个子菜单private static DecimalFormat df = new DecimalFormat("#0.00");// 格式：保留小数点后两位private static boolean judge_01 = false, judge_02 = false;  // 一个小数点按下标志，一个运算符按下标志 public Calculator(){// 重写构造器，相当于初始化JFrame fm = new JFrame("计算器");// 建立框架fm.setBounds(600, 200, 280, 280);// 框架位置和大小JMenuBar mb = new JMenuBar();// 菜单栏mb.setBackground(Color.LIGHT_GRAY);// 菜单栏颜色//mb.setBounds(600, 200, 300, 220);fm.setJMenuBar(mb);// 菜单栏放到框架中// 3个菜单组件oprt = new JMenu("操作");help = new JMenu("帮助");edit = new JMenu("编辑");mb.add(oprt); mb.add(help); mb.add(edit);// 5个子菜单copy = new JMenuItem("复制");paste = new JMenuItem("粘贴");cut = new JMenuItem("剪切");about = new JMenuItem("关于计算器");exit = new JMenuItem("退出");oprt.add(copy); oprt.add(paste); oprt.add(cut); help.add(about); edit.add(exit); // 两个面板，一个流式布局，一个网格布局JPanel pl_01 = new JPanel();JPanel pl_02 = new JPanel();pl_01.setLayout(new FlowLayout());pl_02.setLayout(new GridLayout(5, 4, 6, 6));// 显示text_01 = new JTextArea(2, 27);text_01.setFont(new Font("黑体", Font.BOLD, 16));pl_01.add(text_01);fm.setContentPane(pl_01);// 面板1放入框架pl_01.add(pl_02);// 面板2放入面板1String a[] = {"del", "+/-", "X^2", "+", "7", "8", "9", "-", "4", "5", "6", "*", "1", "2", "3", "/", "0", ".", "C", "="};// 通过循环建立按钮对象，for(int i = 0; i < a.length; i++){bt[i] = new JButton(a[i]);pl_02.add(bt[i]);bt[i].addActionListener(this);// 监听}// 运算符颜色for(int i = 3; i <= 15; i+=4)bt[i].setForeground(Color.RED);// 主要是针对菜单栏组件的show();fm.setVisible(true);fm.setResizable(true);// 大小不可调fm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);}public static void main(String[] args){// 初始化new Calculator();}public void actionPerformed(ActionEvent e){s = e.getActionCommand();// getActionCommand():以字符串形式返回组件名称// 数字按钮按下if("0123456789".indexOf(s) >= 0){text_01.setText(text_01.getText() + s);}// 小数点按钮按下if(e.getSource() == bt[17] && judge_01 == false && text_01.getText().isEmpty() == false){// 前提是有数字按下text_01.setText(text_01.getText() + ".");judge_01 = true;// 第一个小数点按下标志}// 运算符按钮按下if("+-*/".indexOf(s) >= 0 && judge_02 == false && text_01.getText().isEmpty() == false){text_01.setText(text_01.getText() + s);operation();judge_02 = true;// 运算符按下标志}// +/-负号按下if(e.getSource() == bt[1] && text_01.getText() != "0" && text_01.getText().isEmpty() == false){// 正负号按钮按下// 运算符按下之前if(!judge_02){text_01.setText("-"+text_01.getText());}}if(e.getSource() == bt[2]){// 平方按钮按下if(!judge_02){result_01 = Double.parseDouble(text_01.getText());text_01.setText(df.format(result_01*=result_01));}}if(e.getSource() == bt[19]){// 等号按钮按下 equal();}if(e.getSource() == bt[0] && text_01.getText().length() > 0){// 退格按钮按下text_01.setText(text_01.getText().substring(0, text_01.getText().length()-1));// 判断运算符有没有删掉if(text_01.getText().lastIndexOf("+") > 0 || text_01.getText().lastIndexOf("-") > 0 || text_01.getText().lastIndexOf("*") > 0 || text_01.getText().lastIndexOf("/")> 0){judge_02 = true;}else{judge_02 = false; }}if(e.getSource() == bt[18]){// 清空文本text_01.setText("");// 清空文本judge_01 = false;judge_02 = false;}}public static void show(){exit.addMouseListener(new MouseAdapter() {public void mousePressed(MouseEvent e){System.exit(0);}});about.addMouseListener(new MouseAdapter() {public void mousePressed(MouseEvent e){text_02 = new JTextArea();text_02.setText("关于计算器:简单计算器\n设计时间：2017年5月5日\n");JOptionPane.showMessageDialog(null, text_02, "关于计算器", JOptionPane.PLAIN_MESSAGE);}});copy.addMouseListener(new MouseAdapter() {public void mousePressed(MouseEvent e){if(text_01.getText().isEmpty() == false){stemp = text_01.getText();}}});paste.addMouseListener(new MouseAdapter() {public void mousePressed(MouseEvent e){text_01.setText(text_01.getText()+stemp);}});cut.addMouseListener(new MouseAdapter() {public void mousePressed(MouseEvent e){if(text_01.getText().isEmpty() == false){stemp = text_01.getText();text_01.setText("");}}});}public static void operation(){// 运算符按下时，将运算符前的字符保存成double暂存在result_01result_01 = Double.parseDouble(text_01.getText().substring(0, text_01.getText().length()-1));if(s.equals("+"))n = 0;if(s.equals("-"))n = 1;if(s.equals("*"))n = 2;if(s.equals("/"))n = 3;}public static void equal(){if(n == 0){// 加号按下// temp找到“+”所在下标，下标后面就是被加数，被加数保存到tempret中temp = text_01.getText().indexOf("+");if(temp < text_01.getText().length()-1){tempret = Double.parseDouble(text_01.getText().substring(temp+1,text_01.getText().length()));//System.out.println(result_01);result_01+= tempret;s = df.format(result_01);// 格式统一}else// 如果按下“+”，但是没有被加数时，显示“格式错误”,s = "格式错误";//System.out.println(tempret);}else if(n == 1){if(temp < text_01.getText().length()-1){//indexOf(int ch, int fromIndex) 返回指定字符索引，从指定位置搜索temp = text_01.getText().indexOf("-", 1);// lastindexOf从后面搜索也可以tempret = Double.parseDouble(text_01.getText().substring(temp+1,text_01.getText().length()));result_01-= tempret;s = df.format(result_01);}elses = "格式错误";}else if(n == 2){if(temp < text_01.getText().length()-1){temp = text_01.getText().indexOf("*");tempret = Double.parseDouble(text_01.getText().substring(temp+1,text_01.getText().length()));//System.out.println(result_01);result_01*= tempret;s = df.format(result_01);}elses = "格式错误";}else if(n == 3){if(temp < text_01.getText().length()-1){temp = text_01.getText().indexOf("/");tempret = Double.parseDouble(text_01.getText().substring(temp+1,text_01.getText().length()));//System.out.println(result_01);result_01/= tempret;s = df.format(result_01);}elses = "格式错误";}else {// 这是运算符也没按下的情况，比如按下56，则=56s = text_01.getText(); }n = -1;// 运算符按下标志取消//s = df.format(result_01);text_01.setText(text_01.getText()+" = "+s);}}