java计算器源代码

案例剖析

1. 使用图形的方式借助窗口、菜单、按钮等标准界面元素和鼠标操作，来帮助用户方便地向计算机系统发出命令，启动操作，并将系统运行的结果同样以图形的方式显示给用户，这样更加直观和生动；
2. Applet容器中组件的添加与设置，包括面板以及菜单的使用；
3. 容器中组件的布局管理；
4. Java核心包中数组、数学计算类的使用；
5. 异常的处理；
6. 事件处理模型中的三类对象的使用：
   1. Event-事件，用户对界面操作在java语言上的描述，以类的形式出现，例如键盘操作对应的事件类是KeyEvent。
   2. Event Source-事件源，事件发生的场所，通常就是各个组件，例如按钮Button。
   3. Event handler-事件处理者，接收事件对象并对其进行处理的对象。
7. 程序中事件处理的流程：

1. 计算流程的细化

参考代码

import java.awt.*;
import java.lang.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
import java.text.DecimalFormat;
public class Calculator
    implements ActionListener { //导入动作监听接口
  //设计面板中的单位
  JFrame frame;
  JTextField textAnswer;
  JPanel panel, panel1, panel2, panel3;
  JMenuBar mainMenu;
  JTextField textMemory;
  JLabel labelMemSpace; //labelMemSpace单纯做摆设，控制面板的形状
  JButton buttonBk, buttonCe, buttonC;
  JButton button[];
  JButton buttonMC, buttonMR, buttonMS, buttonMAdd;
  JButton buttonDot, buttonAddAndSub, buttonAdd, buttonSub, buttonMul,
      buttonDiv, buttonMod;
  JButton buttonSqrt, buttonDao, buttonEqual;
  JMenu editMenu, viewMenu, helpMenu;
  JMenuItem copyItem, pasteItem, tItem, sItem, numberGroup, topHelp, aboutCal;
  DecimalFormat df; //设置数据输出精度
  boolean clickable; //控制当前能否按键
  double memoryd; //使用内存中存储的数字
  int memoryi;
  double vard, answerd; //用来保存double型数据的中间值(vard)和最后结果(answerd)
  short key = -1, prekey = -1; //key用来保存当前进行何种运算,prekey用来保存前次进行何种运算
  String copy; //做复制用
  JTextArea help; //帮助
  JScrollPane scrollHelp;
  //构造函数
  public Calculator() {
    clickable = true;
    answerd = 0;
    frame = new JFrame("计算器");
    df = new DecimalFormat("0.##############"); //设置数据输出精度(对于double型值)
    textAnswer = new JTextField(15);
    textAnswer.setText("");
    textAnswer.setEditable(false);
    textAnswer.setBackground(new Color(255, 255, 255));
    panel = new JPanel();
    frame.getContentPane().add(panel);
    panel1 = new JPanel();
    panel2 = new JPanel();
    panel.setLayout(new BorderLayout());
    //设计整个面板
    mainMenu = new JMenuBar();
    editMenu = new JMenu("编辑(E)");
    viewMenu = new JMenu("查看(V)");
    helpMenu = new JMenu("帮助(H)");
    copyItem = new JMenuItem("   复制(C) Ctrl+C");
    copyItem.addActionListener(this);
    pasteItem = new JMenuItem("   粘贴(V) Ctrl+V");
    pasteItem.addActionListener(this);
    editMenu.add(copyItem);
    editMenu.add(pasteItem);
    tItem = new JMenuItem("●标准型(T)");
    tItem.addActionListener(this);
    sItem = new JMenuItem("   科学型(S)");
    sItem.addActionListener(this);
    numberGroup = new JMenuItem("   数字分组(I)");
    numberGroup.addActionListener(this);
    viewMenu.add(tItem);
    viewMenu.add(sItem);
    viewMenu.add(numberGroup);
    topHelp = new JMenuItem("   帮助主题(H)");
    topHelp.addActionListener(this);
    help = new JTextArea(5, 20);
    scrollHelp = new JScrollPane(help);
    help.setEditable(false);
    help.append("执行简单计算\n");
    help.append("1.  键入计算的第一个数字。\n");
    help.append("2.  单击“+”执行加、“-”执行减、“*”执行乘或“/”执行除。\n");
    help.append("3.  键入计算的下一个数字。\n");
    help.append("4.  输入所有剩余的运算符和数字。\n");
    help.append("5.  单击“=”。\n");
    aboutCal = new JMenuItem("   关于计算器(A)");
    aboutCal.addActionListener(this);
    helpMenu.add(topHelp);
    helpMenu.add(aboutCal);
    mainMenu.add(editMenu);
    mainMenu.add(viewMenu);
    mainMenu.add(helpMenu);
    panel.add(mainMenu, BorderLayout.NORTH);
    panel.add(textAnswer, BorderLayout.CENTER);
    panel.add(panel1, BorderLayout.SOUTH);
    panel1.setLayout(new BorderLayout());
    textMemory = new JTextField(3);
    textMemory.setEditable(false);
    textMemory.setBackground(new Color(217, 217, 217));
    labelMemSpace = new JLabel("                   ");
    buttonBk = new JButton("Backspace");
    buttonBk.setForeground(new Color(255, 0, 0));
    buttonCe = new JButton("CE");
    buttonCe.setForeground(new Color(255, 0, 0));
    buttonC = new JButton("C");
    buttonC.setForeground(new Color(255, 0, 0));
    buttonBk.addActionListener(this);
    buttonCe.addActionListener(this);
    buttonC.addActionListener(this);
    panel1.add(panel2, BorderLayout.NORTH);
    panel2.setLayout(new FlowLayout(FlowLayout.RIGHT));
    panel2.add(textMemory);
    panel2.add(labelMemSpace);
    panel2.add(buttonBk);
    panel2.add(buttonCe);
    panel2.add(buttonC);
    panel3 = new JPanel();
    panel1.add(panel3, BorderLayout.CENTER);
    button = new JButton[10];
    for (int i = 0; i < button.length; i++) {
      button[i] = new JButton(Integer.toString(i));
      button[i].setForeground(new Color(0, 0, 255));
    }
    buttonMC = new JButton("MC");
    buttonMC.setForeground(new Color(255, 0, 0));
    buttonMR = new JButton("MR");
    buttonMR.setForeground(new Color(255, 0, 0));
    buttonMS = new JButton("MS");
    buttonMS.setForeground(new Color(255, 0, 0));
    buttonMAdd = new JButton("M+");
    buttonMAdd.setForeground(new Color(255, 0, 0));
    buttonDot = new JButton(".");
    buttonDot.setForeground(new Color(0, 0, 255));
    buttonAddAndSub = new JButton("+/-");
    buttonAddAndSub.setForeground(new Color(0, 0, 255));
    buttonAdd = new JButton("+");
    buttonAdd.setForeground(new Color(255, 0, 0));
    buttonSub = new JButton("-");
    buttonSub.setForeground(new Color(255, 0, 0));
    buttonMul = new JButton("*");
    buttonMul.setForeground(new Color(255, 0, 0));
    buttonDiv = new JButton("/");
    buttonDiv.setForeground(new Color(255, 0, 0));
    buttonMod = new JButton("%");
    buttonMod.setForeground(new Color(0, 0, 255));
    buttonSqrt = new JButton("sqrt");
    buttonSqrt.setForeground(new Color(0, 0, 255));
    buttonDao = new JButton("1/x");
    buttonDao.setForeground(new Color(0, 0, 255));
    buttonEqual = new JButton("=");
    buttonEqual.setForeground(new Color(255, 0, 0));
    //将所有行为与监听绑定
    panel3.setLayout(new GridLayout(4, 6));
    panel3.add(buttonMC);
    buttonMC.addActionListener(this);
    panel3.add(button[7]);
    button[7].addActionListener(this);
    panel3.add(button[8]);
    button[8].addActionListener(this);
    panel3.add(button[9]);
    button[9].addActionListener(this);
    panel3.add(buttonDiv);
    buttonDiv.addActionListener(this);
    panel3.add(buttonSqrt);
    buttonSqrt.addActionListener(this);
    panel3.add(buttonMR);
    buttonMR.addActionListener(this);
    panel3.add(button[4]);
    button[4].addActionListener(this);
    panel3.add(button[5]);
    button[5].addActionListener(this);
    panel3.add(button[6]);
    button[6].addActionListener(this);
    panel3.add(buttonMul);
    buttonMul.addActionListener(this);
    panel3.add(buttonMod);
    buttonMod.addActionListener(this);
    panel3.add(buttonMS);
    buttonMS.addActionListener(this);
    panel3.add(button[1]);
    button[1].addActionListener(this);
    panel3.add(button[2]);
    button[2].addActionListener(this);
    panel3.add(button[3]);
    button[3].addActionListener(this);
    panel3.add(buttonSub);
    buttonSub.addActionListener(this);
    panel3.add(buttonDao);
    buttonDao.addActionListener(this);
    panel3.add(buttonMAdd);
    buttonMAdd.addActionListener(this);
    panel3.add(button[0]);
    button[0].addActionListener(this);
    panel3.add(buttonAddAndSub);
    buttonAddAndSub.addActionListener(this);
    panel3.add(buttonDot);
    buttonDot.addActionListener(this);
    panel3.add(buttonAdd);
    buttonAdd.addActionListener(this);
    panel3.add(buttonEqual);
    buttonEqual.addActionListener(this);
    frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
    frame.pack();
    frame.show();
  }
  //设置各个按钮行为
  public void actionPerformed(ActionEvent event) {
    boolean sign = false; //判断是否是double型数参与运算，是为true，不是为false
    Object temp = event.getSource();
    try {
      //如果按下数据按钮，将按下的按钮代表的数据插入的当前文本框字符串之后
      for (int i = 0; i <= 9; i++)
        if (temp == button[i] && clickable == true)
          textAnswer.setText(textAnswer.getText() + Integer.toString(i));
          //按下'.'按钮时，判断当前文本框内字符串中含不含'.'，如果已含，则不允许再插入'.'
      if (temp == buttonDot && clickable == true) {
        boolean isDot = false;
        if (textAnswer.getText().length() == 0)
          isDot = true;
        for (int i = 0; i < textAnswer.getText().length(); i++)
          if ('.' == textAnswer.getText().charAt(i)) {
            isDot = true;
            break;
          }
        if (isDot == false)
          textAnswer.setText(textAnswer.getText() + ".");
      }
      if ( (temp == buttonAdd || temp == buttonSub || temp == buttonMul ||
            temp == buttonDiv) && clickable == true) {
        //'+'操作
        if (temp == buttonAdd) {
          switch (prekey) {
            case 0:
              answerd += Double.parseDouble(textAnswer.getText());
              break;
            case 1:
              answerd -= Double.parseDouble(textAnswer.getText());
              break;
            case 2:
              answerd *= Double.parseDouble(textAnswer.getText());
              break;
            case 3:
              if (Double.parseDouble(textAnswer.getText()) == 0) {
                textAnswer.setText("除数不能为零");
                clickable = false;
              }
              else
                answerd /= Double.parseDouble(textAnswer.getText());
              break;
            default:
              answerd = Double.parseDouble(textAnswer.getText());
          }
          textAnswer.setText("");
          prekey = key = 0;
        }
        //'-'操作
        if (temp == buttonSub) {
          switch (prekey) {
            case 0:
              answerd += Double.parseDouble(textAnswer.getText());
              break;
            case 1:
              answerd -= Double.parseDouble(textAnswer.getText());
              break;
            case 2:
              answerd *= Double.parseDouble(textAnswer.getText());
              break;
            case 3:
              if (Double.parseDouble(textAnswer.getText()) == 0) {
                textAnswer.setText("除数不能为零");
                clickable = false;
              }
              else
                answerd /= Double.parseDouble(textAnswer.getText());
              break;
            default:
              answerd = Double.parseDouble(textAnswer.getText());
          }
          textAnswer.setText("");
          prekey = key = 1;
        }
        //'*'操作
        if (temp == buttonMul) {
          switch (prekey) {
            case 0:
              answerd += Double.parseDouble(textAnswer.getText());
              break;
            case 1:
              answerd -= Double.parseDouble(textAnswer.getText());
              break;
            case 2:
              answerd *= Double.parseDouble(textAnswer.getText());
              break;
            case 3:
              if (Double.parseDouble(textAnswer.getText()) == 0) {
                textAnswer.setText("除数不能为零");
                clickable = false;
              }
              else
                answerd /= Double.parseDouble(textAnswer.getText());
              break;
            default:
              answerd = Double.parseDouble(textAnswer.getText());
          }
          textAnswer.setText("");
          prekey = key = 2;
        }
        //'/'操作
        if (temp == buttonDiv) {
          switch (prekey) {
            case 0:
              answerd += Double.parseDouble(textAnswer.getText());
              break;
            case 1:
              answerd -= Double.parseDouble(textAnswer.getText());
              break;
            case 2:
              answerd *= Double.parseDouble(textAnswer.getText());
              break;
            case 3:
              if (Double.parseDouble(textAnswer.getText()) == 0) {
                textAnswer.setText("除数不能为零");
                clickable = false;
              }
              else
                answerd /= Double.parseDouble(textAnswer.getText());
              break;
            default:
              answerd = Double.parseDouble(textAnswer.getText());
          }
          textAnswer.setText("");
          prekey = key = 3;
        }
      }
      //'='操作
      if (temp == buttonEqual && clickable == true) {
        //如果连续按'=',则进行连续运算
        if (prekey == 5) {
          if (key == 0) {
            answerd += vard;
            textAnswer.setText(df.format(answerd));
          }
          if (key == 1) {
            answerd -= vard;
            textAnswer.setText(df.format(answerd));
          }
          if (key == 2) {
            answerd *= vard;
            textAnswer.setText(df.format(answerd));
          }
          if (key == 3) {
            if (Double.parseDouble(textAnswer.getText()) == 0) {
              textAnswer.setText("除数不能为零");
              clickable = false;
            }
            else {
              answerd /= vard;
              textAnswer.setText(df.format(answerd));
            }
          }
        }
        else {
          vard = Double.parseDouble(textAnswer.getText());
          if (key == 0) {
            prekey = -1;
            answerd += Double.parseDouble(textAnswer.getText());
            textAnswer.setText(df.format(answerd));
          }
          if (key == 1) {
            prekey = -1;
            answerd -= Double.parseDouble(textAnswer.getText());
            textAnswer.setText(df.format(answerd));
          }
          if (key == 2) {
            prekey = -1;
            answerd *= Double.parseDouble(textAnswer.getText());
            textAnswer.setText(df.format(answerd));
          }
          if (key == 3) {
            prekey = -1;
            if (Double.parseDouble(textAnswer.getText()) == 0) {
              textAnswer.setText("除数不能为零");
              clickable = false;
            }
            else {
              answerd /= Double.parseDouble(textAnswer.getText());
              textAnswer.setText(df.format(answerd));
            }
          }
        }
        prekey = 5;
      }
      //'%'操作，对第二个操作数除以100
      if (temp == buttonMod && clickable == true) {
        if (answerd == 0) {
          String s = textAnswer.getText();
          textAnswer.setText(s);
        }
        else {
          boolean isDot = false;
          for (int i = 0; i < textAnswer.getText().length(); i++)
            if ('.' == textAnswer.getText().charAt(i)) {
              isDot = true;
              break;
            }
          //如果是double数，除100
          if (isDot == true) {
            double dtemp = Double.parseDouble(textAnswer.getText());
            dtemp = dtemp / 100.0;
            textAnswer.setText(Double.toString(dtemp));
          }
          else {
            //如果是int数但能被100整除，则去掉末尾两个零
            if (Integer.parseInt(textAnswer.getText()) % 100 == 0) {
              int itemp = Integer.parseInt(textAnswer.getText());
              itemp /= 100;
              textAnswer.setText(Integer.toString(itemp));
            }
            //如果是int数，但不能被100整除，则按double数处理
            else {
              double dtemp = Double.parseDouble(textAnswer.getText());
              dtemp = dtemp / 100.0;
              textAnswer.setText(Double.toString(dtemp));
            }
          }
        }
      }
      //开根号运算
      if (temp == buttonSqrt && clickable == true) {
        String s = textAnswer.getText();
        if (s.charAt(0) == '-') {
          textAnswer.setText("负数不能开根号");
          clickable = false;
        }
        else
          textAnswer.setText(Double.toString(java.lang.Math.sqrt(Double.
              parseDouble(textAnswer.getText()))));
      }
      //倒数运算
      if (temp == buttonDao && clickable == true) {
        if (textAnswer.getText().charAt(0) == '0' &&
            textAnswer.getText().length() == 1) {
          textAnswer.setText("零不能求倒数");
          clickable = false;
        }
        else {
          boolean isDec = true;
          int i, j, k;
          String s = Double.toString(1 / Double.parseDouble(textAnswer.getText()));
          for (i = 0; i < s.length(); i++)
            if (s.charAt(i) == '.')
              break;
          for (j = i + 1; j < s.length(); j++)
            if (s.charAt(j) != '0') {
              isDec = false;
              break;
            }
          if (isDec == true) {
            String stemp = "";
            for (k = 0; k < i; k++)
              stemp += s.charAt(k);
            textAnswer.setText(stemp);
          }
          else
            textAnswer.setText(s);
        }
      }
      //按下'+/-'按钮时处理
      if (temp == buttonAddAndSub && clickable == true) {
        boolean isNumber = true;
        String s = textAnswer.getText();
        for (int i = 0; i < s.length(); i++)
          if (! (s.charAt(i) >= '0' && s.charAt(i) <= '9' || s.charAt(i) == '.' ||
                 s.charAt(i) == '-')) {
            isNumber = false;
            break;
          }
        if (isNumber == true) {
          //如果当前字符串首字母有'-'号,代表现在是个负数,再按下时,则将首符号去掉
          if (s.charAt(0) == '-') {
            textAnswer.setText("");
            for (int i = 1; i < s.length(); i++) {
              char a = s.charAt(i);
              textAnswer.setText(textAnswer.getText() + a);
            }
          }
          //如果当前字符串第一个字符不是符号，则添加一个符号在首字母处
          else
            textAnswer.setText('-' + s);
        }
      }
      //计算器有关内存操作
      //'MC'的操作，将内存清0
      if (temp == buttonMC && clickable == true) {
        memoryd = memoryi = 0;
        textMemory.setText("");
      }
      //'MS'的操作，将当前文本框内容保存入内存，显示'M'
      if (temp == buttonMS && clickable == true) {
        boolean isDot = false;
        textMemory.setText("   M");
        for (int i = 0; i < textAnswer.getText().length(); i++)
          if ('.' == textAnswer.getText().charAt(i)) {
            isDot = true;
            break;
          }
        //如果是double,则存入memoryd(double存储器)
        if (isDot == true) {
          memoryd = Double.parseDouble(textAnswer.getText());
          memoryi = 0; //保证存储器中存放最新的值
        }
        //如果是int,则存入memoryi(int存储器)
        else {
          memoryi = Integer.parseInt(textAnswer.getText());
          memoryd = 0; //保证存储器中存放最新的值
        }
      }
      //'MR'的操作，将存储器中的信息输出
      if (temp == buttonMR && clickable == true) {
        if (memoryd != 0)
          textAnswer.setText(Double.toString(memoryd));
        if (memoryi != 0)
          textAnswer.setText(Integer.toString(memoryi));
      }
      //'M+'的功能，将当前文本框里的数据和存储器中数据相加后，再存入存储器
      if (temp == buttonMAdd && clickable == true) {
        boolean isDot = false;
        for (int i = 0; i < textAnswer.getText().length(); i++)
          if ('.' == textAnswer.getText().charAt(i)) {
            isDot = true;
            break;
          }
        if (memoryi != 0) { //存储中是一个int型数
          if (isDot == false) //被加数是一个int型数
            memoryi += Integer.parseInt(textAnswer.getText());
          else { //被加数是一个double型数，则将int存储器中数传入double存储器与当前数相加，int存储器清零
            memoryd = memoryi + Double.parseDouble(textAnswer.getText());
            memoryi = 0;
          }
        }
        else
          memoryd += Double.parseDouble(textAnswer.getText());
      }
      //按下'Backspace'键，利用循环将当前字符串中的最后一个字母删除
      if (temp == buttonBk && clickable == true) {
        String s = textAnswer.getText();
        textAnswer.setText("");
        for (int i = 0; i < s.length() - 1; i++) {
          char a = s.charAt(i);
          textAnswer.setText(textAnswer.getText() + a);
        }
      }
      //按下'CE'按钮，将当前文本框内数据清除
      if (temp == buttonCe) {
        textAnswer.setText("");
        clickable = true;
      }
      //按下'C'按钮，文本框内数据清除，同时var,answer清0
      if (temp == buttonC) {
        vard = answerd = 0;
        textAnswer.setText("");
        clickable = true;
      }
      //按下'复制'菜单栏
      if (temp == copyItem) {
        copy = textAnswer.getText();
      }
      //按下'粘贴'菜单栏
      if (temp == pasteItem) {
        textAnswer.setText(copy);
      }
      if (temp == sItem) {
        JOptionPane.showMessageDialog(panel, "当前是标准型计算器，\n科学型计算器有待更新。");
      }
      //按下'帮助主题'菜单栏
      if (temp == topHelp) {
        JOptionPane.showMessageDialog(panel, scrollHelp);
      }
      //按下'数字分组'菜单栏
      if (temp == numberGroup) {
        if (numberGroup.getText().compareTo("   数字分组(I)") == 0)
          numberGroup.setText("√数字分组(I)");
        else
          numberGroup.setText("   数字分组(I)");
      }
      //按下'关于'菜单栏
      if (temp == aboutCal) {
        JOptionPane.showMessageDialog(panel, "计算器1.00版\n开发者：楼竞");
      }
    }
    //输入中如果有操作非法，比如按下两次'+'，捕获异常
    catch (Exception e) {
      textAnswer.setText("操作非法");
      clickable = false;
    }
  }
  //主函数
  public static void main(String args[]) {
    new Calculator();
  }
}