求java计算器代码 要有键盘事件响应的

Question

学java第二学期  在使用jbuilder 但书上的代码断断续续  看不太懂 所以来论坛里求助

Answer 1

我赞成你自己写，错了可以改不是问题，不会写可以边学边写也不是问题
很惭愧，我这学期才接触Java（也就是刚好两个月），但是我觉得真要把一种语言学好的话始终是要自己动手的，否则即使你看再多的代码，找再多的人帮你也于事无补
一起加油吧

Answer 2

刚学Java才2个星期，这个计算器的代码边学边写，总是不会怎么样把键盘操作给实现了。惭愧

Answer 3

csdn的兄弟们就是专业，这里是解决疑难杂症的地方，大家不会主张帮你完成，都希望你能自己提高，很喜欢csdn这种风格。

Answer 4

public void this_keyPressed(KeyEvent e) {
        if(e.getKeyCode()==KeyEvent.VK_NUMPAD0)
            JOptionPane.showMessageDialog(this,"你按下了键盘上的数字0");
         else  if(e.getKeyCode()==KeyEvent.VK_NUMPAD1)
          JOptionPane.showMessageDialog(this,"你按下了键盘上的数字1");
        // else if(.......)
    }

Answer 5

这也是别人的代码，仅供参考import java.awt.*;
import java.io.*;
import java.lang.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
import java.text.DecimalFormat;
public class Calculator implements ActionListener,KeyListener{
   public static void main(String args[]) {
    new Calculator();
  }
  JFrame frame;
  JTextField textAnswer;
  JTextArea help;
  JPanel panel,panel1,panel2,panel3,panel4;
  JButton button[];
  JButton buttonAdd,buttonEqual,buttonDot,buttonSub,buttonDiv,buttonMul;
  JButton buttonBk, buttonCe, buttonC;
  double num1,num2;
  double answer;
  boolean intflag=true;
  boolean operatorflag=true;
  boolean equalflag=true;
  int key;
  DecimalFormat df;
 
  public Calculator() {
    df = new DecimalFormat("0.##############"); //设置数据输出精度(对于double型值)
    frame = new JFrame("LT.的计算器");
    frame.setResizable(false);
    Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
    int x = (dim.width)/2-150;
    int y = (dim.height)/2-250;
    frame.setLocation(x,y); //设置窗口位置
    panel=new JPanel();
    textAnswer=new JTextField(15);
    textAnswer.setText("");
    textAnswer.setHorizontalAlignment(SwingConstants.RIGHT);
    textAnswer.setEditable(false);
    textAnswer.setBackground(new Color(255,255,255));
    textAnswer.addKeyListener(this);
    frame.getContentPane().add(panel);
    panel.setLayout(new BorderLayout());
    panel2=new JPanel();
   
    panel4=new JPanel();
    panel.add(panel4,BorderLayout.CENTER);
    panel4.setLayout(new BorderLayout());
    panel3=new JPanel();
    panel4.add(panel3,BorderLayout.CENTER);
    buttonBk=new JButton("BackSpace");
    panel3.add(buttonBk);
    buttonBk.addActionListener(this);
    buttonBk.addKeyListener(this);
    buttonCe=new JButton("CE");
    panel3.add(buttonCe);
    buttonCe.addActionListener(this);
    buttonCe.addKeyListener(this);
    buttonC=new JButton("C");
    panel3.add(buttonC);
    buttonC.addActionListener(this);
    buttonC.addKeyListener(this);
    panel.add(textAnswer,BorderLayout.NORTH);
    panel.add(panel2,BorderLayout.WEST);    panel1=new JPanel();
    panel4.add(panel1,BorderLayout.SOUTH);
    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));
    }
    buttonAdd=new JButton("+");
    buttonSub=new JButton("-");
    buttonDiv=new JButton("/");
    buttonMul=new JButton("*");
    buttonDot=new JButton(".");
    buttonEqual=new JButton("=");
    panel1.setLayout(new GridLayout(4,4));
    panel1.add(button[7]);
    button[7].addActionListener(this);
    button[7].addKeyListener(this);
    panel1.add(button[8]);
    button[8].addActionListener(this);
    button[8].addKeyListener(this);
    panel1.add(button[9]);
    button[9].addActionListener(this);
    button[9].addKeyListener(this);
    panel1.add(buttonAdd);
    buttonAdd.addActionListener(this);
    buttonAdd.addKeyListener(this);
    panel1.add(button[4]);
    button[4].addActionListener(this);
    button[4].addKeyListener(this);
    panel1.add(button[5]);
    button[5].addActionListener(this);
    button[5].addKeyListener(this);
    panel1.add(button[6]);
    button[6].addActionListener(this);
    button[6].addKeyListener(this);
    panel1.add(buttonSub);
    buttonSub.addActionListener(this);
    panel1.add(button[1]);
    button[1].addActionListener(this);
    button[1].addKeyListener(this);
    panel1.add(button[2]);
    button[2].addActionListener(this);
    button[2].addKeyListener(this);
    panel1.add(button[3]);
    button[3].addActionListener(this);
    button[3].addKeyListener(this);
    panel1.add(buttonMul);
    buttonMul.addActionListener(this);
    buttonMul.addKeyListener(this);
    panel1.add(button[0]);
    button[0].addActionListener(this);
    button[0].addKeyListener(this);
    panel1.add(buttonDot);
    buttonDot.addActionListener(this);
    buttonDot.addKeyListener(this);
    panel1.add(buttonEqual);
    buttonEqual.addActionListener(this);
    buttonEqual.addKeyListener(this);
    panel1.add(buttonDiv);
    buttonDiv.addActionListener(this);
    buttonDiv.addKeyListener(this);
    //buttonAdd.setFocusable(true);
    frame.addKeyListener(this);
    frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
    frame.pack();
    frame.show();
  }
    public void keyPressed(KeyEvent e){
          int i=e.getKeyCode();
          char c=e.getKeyChar();
          if(i==KeyEvent.VK_ADD){
                Add();
          }
          else if(i==KeyEvent.VK_SUBTRACT){
                 Sub();
          }
          else if(i==KeyEvent.VK_DIVIDE){
                 Div();
          }
          else if(i==KeyEvent.VK_MULTIPLY){
                 Mul();
          }
          else if(i==KeyEvent.VK_ENTER){
                  Enter();
          }
          else if(c=='.'){
                  Dot();
          }
          else if(i==KeyEvent.VK_BACK_SPACE){
                  Backspace();
          }
          else if(i==KeyEvent.VK_Q){
                  clear();
          }
          Input(c);
    }
   public void keyReleased(KeyEvent e) {
  // TODO 自动生成方法存根
 }
 public void keyTyped(KeyEvent e) {
  // TODO 自动生成方法存根
 }
 
  //设置各个按钮行为
  public void actionPerformed(ActionEvent event) {
    Object temp = event.getSource();
    //boolean operatorflag=true;
    if(temp==KeyStroke.getKeyStroke('f')){
          temp=button[1];
    }
    try{
       for(int i=0;i<10;i++)
          Input(temp,i);
       if(temp==buttonAdd||temp==buttonMul||temp==buttonDiv||temp==buttonSub){
          if(temp==buttonAdd){
              Add();
          }
          if(temp==buttonSub){
             Sub();
          }
          if(temp==buttonMul){
             Mul();
           }
           if(temp==buttonDiv){
              Div();
           }
       }
       if(temp==buttonEqual){
          Enter();
       }
       if(temp==buttonC){
          clear();
       }
       if(temp==buttonBk){
          Backspace();
       }
       if(temp==buttonDot){
          Dot();
       }    }
    catch(Exception e){
       textAnswer.setText("非法操作");
    }
  }
  public void culcator(Exception e){
  }
  
 

Answer 6

public void Input(char c){
     int i=c-48;
     if(i<0||i>9)
         return;
     if(operatorflag&&equalflag){
              textAnswer.setText(textAnswer.getText()+Integer.toString(i));
              frame.setTitle(frame.getTitle()+Integer.toString(i));
          }
          else if(operatorflag==false&&!equalflag){
              textAnswer.setText("");
              textAnswer.setText(textAnswer.getText()+Integer.toString(i));
              frame.setTitle("LT.的计算器"+Integer.toString(i));
              operatorflag=true;
              equalflag=true;
          }
          else if(operatorflag&&!equalflag){
              textAnswer.setText("");
              equalflag=true;
              textAnswer.setText(textAnswer.getText()+Integer.toString(i));
              frame.setTitle(frame.getTitle()+Integer.toString(i));
              }
  }
  public void Input(Object temp,int i){
       if(temp==button[i]&&operatorflag&&equalflag){
              textAnswer.setText(textAnswer.getText()+Integer.toString(i));
              frame.setTitle(frame.getTitle()+Integer.toString(i));
          }
          else if(temp==button[i]&&operatorflag==false&&!equalflag){
              textAnswer.setText("");
              textAnswer.setText(textAnswer.getText()+Integer.toString(i));
              frame.setTitle("LT.的计算器"+Integer.toString(i));
              operatorflag=true;
              equalflag=true;
          }
          else if(temp==button[i]&&operatorflag&&!equalflag){
              textAnswer.setText("");
              equalflag=true;
              textAnswer.setText(textAnswer.getText()+Integer.toString(i));
              frame.setTitle(frame.getTitle()+Integer.toString(i));
              }
     }
   public void Add(){
      if(intflag==true){
                 num1=Double.parseDouble(textAnswer.getText());
             }
             textAnswer.setText("+");
             operatorflag=true;
             equalflag=false;
             key=1;
      if(answer==0)
          frame.setTitle("LT.的计算器"+df.format(num1)+"+");
   }
   public void Sub(){
      if(intflag==true){
                 num1=Double.parseDouble(textAnswer.getText());
      }
      textAnswer.setText("-");
      operatorflag=true;
      equalflag=false;
      key=2;
      if(answer==0)
          frame.setTitle("LT.的计算器"+df.format(num1)+"-");
   }
   public void Div(){
      if(intflag==true){
                 num1=Double.parseDouble(textAnswer.getText());
              }
             textAnswer.setText("/");
             operatorflag=true;
             equalflag=false;
             key=4;
      if(answer==0)
          frame.setTitle("LT.的计算器"+df.format(num1)+"/");
  }
  public void Mul(){
      if(intflag==true){
                 num1=Double.parseDouble(textAnswer.getText());
              }
             textAnswer.setText("*");
             operatorflag=true;
             equalflag=false;
             key=3;
      if(answer==0)
          frame.setTitle("LT.的计算器"+df.format(num1)+"*");
  }
  public void Enter(){
     num2=Double.parseDouble(textAnswer.getText());
     char c='+';
          switch(key){
             case 1:
               answer=num1+num2;
               textAnswer.setText(df.format(answer));
               operatorflag=false;
               equalflag=false;
               c='+';
               break;
             case 2:
               answer=num1-num2;
               textAnswer.setText(df.format(answer));
               operatorflag=false;
               equalflag=false;
               c='-';
               break;
             case 3:
               answer=num1*num2;
               textAnswer.setText(df.format(answer));
               operatorflag=false;
               equalflag=false;
               c='*';
               break;
             case 4:
               answer=num1/num2;
               textAnswer.setText(df.format(answer));
               operatorflag=false;
               equalflag=false;
               c='/';
               break;
          }
          double n1=num1;
          double n2=num2;
          num2=0;
          num1=answer;
          answer=0;
          frame.setTitle("LT.的计算器"+df.format(n1)+c+df.format(n2)+"="+df.format(num1));
  }
  public void Dot(){
       boolean isDot=false;
          for(int i=0;i<textAnswer.getText().length();i++){
              if('.'==textAnswer.getText().charAt(i)){
                  isDot=true;
                  break;
              }
          }
          if(isDot==false){
              textAnswer.setText(textAnswer.getText()+".");
              frame.setTitle(frame.getTitle()+".");
          }
  }
 public void Backspace(){
          String s = textAnswer.getText();
          String t=frame.getTitle();
          frame.setTitle("");
          textAnswer.setText("");
          for (int i = 0; i < s.length() - 1; i++) {
              char a = s.charAt(i);
              textAnswer.setText(textAnswer.getText() + a);
          }
          if(t.length()>7){
              for(int i=0;i<t.length()-1;i++){
                  char b=t.charAt(i);
                  frame.setTitle(frame.getTitle()+b);
              }
           }
           else{
              frame.setTitle("LT.的计算器");
           }
  }
  public void clear(){
          textAnswer.setText("0");
          num1=0;
          num2=0;
          answer=0;
          operatorflag=true;
          equalflag=false;
          frame.setTitle("LT.的计算器");
  }  }

Answer 7

package com.ibm;import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;public class Calculator extends JFrame implements ActionListener, KeyListener {
private JTextField display = new JTextField("0");
// 按钮上的文字
private String buttonText = "789/456*123-0.=+";
// 用来存放按钮对象
private JButton[] btns = new JButton[16]; private double result = 0; private String operator = "="; private boolean calculating = true; public Calculator() {
setLayout(new BorderLayout()); display.setEditable(false);
add(display, "North"); JPanel p = new JPanel();
p.setLayout(new GridLayout(4, 4));
p.setLayout(new GridLayout(4, 4));
for (int i = 0; i < buttonText.length(); i++) {
JButton b = new JButton(buttonText.substring(i, i + 1));
p.add(b);
b.addActionListener(this);
b.addKeyListener(this);
btns[i] = b;
}
add(p, "Center");
this.setFocusable(true);
this.addKeyListener(this); } public void actionPerformed(ActionEvent evt) {
String cmd = evt.getActionCommand();
if ('0' <= cmd.charAt(0) && cmd.charAt(0) <= '9' || cmd.equals(".")) {
if (calculating)
display.setText(cmd);
else
display.setText(display.getText() + cmd);
calculating = false;
} else {
if (calculating) {
if (cmd.equals("-")) {
display.setText(cmd);
calculating = false;
} else
operator = cmd;
} else {
double x = Double.parseDouble(display.getText());
calculate(x);
operator = cmd;
calculating = true;
}
}
} private void calculate(double n) {
if (operator.equals("+"))
result += n;
else if (operator.equals("-"))
result -= n;
else if (operator.equals("*"))
result *= n;
else if (operator.equals("/"))
result /= n;
else if (operator.equals("="))
result = n;
display.setText("" + result);
} // 当小键盘按键按下时
public void keyPressed(KeyEvent e) {
for (JButton btn : btns) {
// 当按下小键盘的回车时，执行”=“
if (e.getKeyCode() == KeyEvent.VK_ENTER) {
btns[14].doClick();
return;
}
if (btn.getText().equals(String.valueOf(e.getKeyChar()))) {
btn.doClick();
}
}
} public void keyReleased(KeyEvent e) {
} public void keyTyped(KeyEvent e) {
} public static void main(String[] args) {
Calculator frame = new Calculator();
frame.setTitle("Calculator");
frame.setSize(200, 200);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

Answer 8

http://woshigaohan.blog.163.com/blog/static/11158338200752355835951/
我以前写的一个计算器，可以参考下，O(∩_∩)O~

Answer 9

我也学JAVA不久，这么多志同道合的朋友一起奋斗着，加油！！！

Answer 10

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import java.util.LinkedList;
import java.io.*;
public class CalculatorWindow extends JFrame implements ActionListener{
    NumberButton numberButton[];                  
    OperationButton operationButton[];             
    JButton 小数点操作,正负号操作,退格操作,等号操作,清零操作,sin;
    JTextField resultShow;          //显示计算结果
    JTextField showComputerProcess; //显示当前计算过程
    JTextArea  saveComputerProcess; //显示计算步骤
    JButton saveButton,copyButton,clearButton;
    LinkedList<String> list;   //链表用来存放第一个运算数、运算符号和第二个运算数
    HandleDigit handleDigit;  //负责处理ActionEvent事件
    HandleOperation handleOperation ;
    HandleBack handleBack;
    HandleClear handleClear;
    HandleEquality handleEquality;
    HandleDot handleDot;
    HandlePOrN handlePOrN;
    HandleSin handleSin;
    public CalculatorWindow(){
        setTitle("计算器");
        JPanel panelLeft,panelRight; 
        list=new LinkedList<String>();
        resultShow=new JTextField(10);
        resultShow.setHorizontalAlignment(JTextField.RIGHT);
        resultShow.setForeground(Color.blue);
        resultShow.setFont(new Font("TimesRoman",Font.BOLD,16));
        resultShow.setBorder(new SoftBevelBorder(BevelBorder.LOWERED));
        resultShow.setEditable(false);
        resultShow.setBackground(Color.white);
        showComputerProcess=new JTextField();
        showComputerProcess.setHorizontalAlignment(JTextField.CENTER);
        showComputerProcess.setFont(new Font("Arial",Font.BOLD,16));
        showComputerProcess.setBackground(Color.cyan);
        showComputerProcess.setEditable(false);
        saveComputerProcess=new JTextArea();
        saveComputerProcess.setEditable(false);
        saveComputerProcess.setFont(new Font("宋体",Font.PLAIN,16));
        numberButton=new NumberButton[10];
        handleDigit=new HandleDigit(list,resultShow,showComputerProcess);
        for(int i=0;i<=9;i++){
            numberButton[i]=new NumberButton(i);
            numberButton[i].setFont(new Font("Arial",Font.BOLD,20));
            numberButton[i].addActionListener(handleDigit);
        }
        operationButton=new OperationButton[4];
        handleOperation=new HandleOperation(list,resultShow,
                         showComputerProcess,saveComputerProcess);
        String 运算符号[]={"+","-","*","/"}; 
        for(int i=0;i<4;i++){
           operationButton[i]=new OperationButton(运算符号[i]);
           operationButton[i].setFont(new Font("Arial",Font.BOLD,20));
           operationButton[i].addActionListener(handleOperation);
        }
       小数点操作=new JButton(".");
       handleDot=new HandleDot(list,resultShow,showComputerProcess);
       小数点操作.addActionListener(handleDot);
       正负号操作=new JButton("+/-"); 
       handlePOrN=new HandlePOrN(list,resultShow,showComputerProcess);
       正负号操作.addActionListener(handlePOrN);
       等号操作=new JButton("=");
       handleEquality=new HandleEquality(list,resultShow,
                                         showComputerProcess,saveComputerProcess);
       等号操作.addActionListener(handleEquality); 
       sin=new JButton("sin");
       handleSin=new HandleSin(list,resultShow,
                               showComputerProcess,saveComputerProcess);
       sin.addActionListener(handleSin);
       退格操作=new JButton("退格");
       handleBack=new HandleBack(list,resultShow,showComputerProcess);
       退格操作.addActionListener(handleBack);
       清零操作=new JButton("C");
       handleClear=new HandleClear(list,resultShow,showComputerProcess);
       清零操作.addActionListener(handleClear); 
       清零操作.setForeground(Color.red);
       退格操作.setForeground(Color.red);
       等号操作.setForeground(Color.red);
       sin.setForeground(Color.blue);
       正负号操作.setForeground(Color.blue);
       小数点操作.setForeground(Color.blue);
       panelLeft=new JPanel(); 
       panelRight=new JPanel();
       panelLeft.setLayout(new BorderLayout()); 
       JPanel centerInLeft=new JPanel();
       panelLeft.add(resultShow,BorderLayout.NORTH);
       panelLeft.add(centerInLeft,BorderLayout.CENTER);
       centerInLeft.setLayout(new GridLayout(4,5)); 
       centerInLeft.add(numberButton[1]);
       centerInLeft.add(numberButton[2]);
       centerInLeft.add(numberButton[3]);
       centerInLeft.add(operationButton[0]);
       centerInLeft.add(清零操作);
       centerInLeft.add(numberButton[4]);
       centerInLeft.add(numberButton[5]);
       centerInLeft.add(numberButton[6]);
       centerInLeft.add(operationButton[1]);
       centerInLeft.add(退格操作);
       centerInLeft.add(numberButton[7]);
       centerInLeft.add(numberButton[8]);
       centerInLeft.add(numberButton[9]);
       centerInLeft.add(operationButton[2]);
       centerInLeft.add(sin);
       centerInLeft.add(numberButton[0]);
       centerInLeft.add(正负号操作);
       centerInLeft.add(小数点操作);
       centerInLeft.add(operationButton[3]);
       centerInLeft.add(等号操作);
       panelRight.setLayout(new BorderLayout());
       panelRight.add(showComputerProcess,BorderLayout.NORTH);
       saveButton=new JButton("保存");
       copyButton=new JButton("复制");
       clearButton=new JButton("清除");
       saveButton.setToolTipText("保存计算过程到文件");
       copyButton.setToolTipText("复制选中的计算过程");
       clearButton.setToolTipText("清除计算过程");
       saveButton.addActionListener(this);
       copyButton.addActionListener(this);
       clearButton.addActionListener(this); 
       panelRight.add(new JScrollPane(saveComputerProcess),BorderLayout.CENTER);
       JPanel southInPanelRight=new JPanel();
       southInPanelRight.add(saveButton);
       southInPanelRight.add(copyButton);
       southInPanelRight.add(clearButton);
       panelRight.add(southInPanelRight,BorderLayout.SOUTH);
       JSplitPane split=new JSplitPane
                (JSplitPane.HORIZONTAL_SPLIT,panelLeft,panelRight);
       add(split,BorderLayout.CENTER);
       setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       setVisible(true);
       setBounds(100,50,528,258);
       validate();
   }
   public void actionPerformed(ActionEvent e){
       if(e.getSource()==copyButton)
          saveComputerProcess.copy();
       if(e.getSource()==clearButton)
          saveComputerProcess.setText(null);
       if(e.getSource()==saveButton){
           JFileChooser chooser=new JFileChooser();
           int state=chooser.showSaveDialog(null);
           File file=chooser.getSelectedFile();
           if(file!=null&&state==JFileChooser.APPROVE_OPTION){
             try{  String content=saveComputerProcess.getText();
                   StringReader read=new StringReader(content);
                   BufferedReader in= new BufferedReader(read);
                   FileWriter outOne=new FileWriter(file);
                   BufferedWriter out= new BufferedWriter(outOne);
                   String str=null;
                   while((str=in.readLine())!=null){
                      out.write(str);
                      out.newLine();
                   }
                  in.close();
                  out.close();
             } 
             catch(IOException e1){}
           }
       }
   }
   public static void main(String args[]){
       new CalculatorWindow();
   }  
}

Answer 11

import java.util.LinkedList;
import javax.swing.*;
import java.awt.event.*;
public class HandleBack implements ActionListener{
    LinkedList<String> list;
    JTextField resultShow,showComputerProcess;          
    HandleBack(LinkedList<String> list,JTextField t1,JTextField t2){
        this.list=list;
        resultShow=t1;
        showComputerProcess=t2; 
    }
    public void actionPerformed(ActionEvent e){
        if(list.size()==1){                               
           String num=(String)list.getFirst();
           if(num.length()>=1){
                 num=num.substring(0,num.length()-1);
                 list.set(0,num);                  
                 resultShow.setText(num);
                 showComputerProcess.setText(""+num);
           }
           else{
                 list.removeLast();                  
                 resultShow.setText("0");
                 showComputerProcess.setText("0");
           }
        }
        else if(list.size()==3){
           String num=(String)list.getLast();
           if(num.length()>=1){
                 num=num.substring(0,num.length()-1);
                 list.set(2,num);                  
                 resultShow.setText(num);
                 showComputerProcess.setText(num);
           }
           else{
                 list.removeLast();                  
                 resultShow.setText("0");
                 showComputerProcess.setText("0");
           }
       }
    }
}

Answer 12

import java.awt.*;
import java.awt.event.*;
import java.math.BigDecimal;
import javax.swing.*;//创建计算器Calculator类，实现ActionListener接口
public class Calculater implements ActionListener
{
//定义变量和按钮数组
private String[] names = {"Backspace","CE","C","+","7","8","9","-",
"4","5","6","*","1","2","3","/","0","+/-",".","="};
private JButton[] buttonArray = new JButton[names.length];
private boolean append = false;//默认追加为false
private String operator = "+";//默认运算符为“+”
private String s1 = "0";//默认字符为0
private String ss = "0";//默认字符为0
//创建可以显示20个字符的文本框
JTextField jtf = new JTextField(20);

//构造方法
public Calculater() {}
public Calculater(String title)
{
//创建窗口、面板，并设置面板布局为网格布局
JFrame jf = new JFrame(title);
JPanel jp = new JPanel();
jp.setLayout(new GridLayout(5,4));
//依次添加按钮到面板中，并为按钮注册监听器
for (int i = 0; i < buttonArray.length; i++)
{
buttonArray[i] = new JButton(names[i]);
buttonArray[i].addActionListener(this);
jp.add(buttonArray[i]);
}
//添加文本框到窗体中
jf.add(jtf,BorderLayout.NORTH);
jf.add(jp);//添加面板到窗体中
jtf.setHorizontalAlignment(JTextField.RIGHT);//设置文本框的水平方向为右
jtf.setText("0");//设置初始文本为0
jtf.setEditable(false);//设置文本框为不可编辑状态
//设置窗体属性
jf.pack();//系统自动设置大小和位置
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

//实现监听接口的actionPerformed方法
public void actionPerformed(ActionEvent e)
{
String comm = e.getActionCommand();
if(comm.matches("\\d")) //用正则表达式判断输出的是否是0~9
{
if(append)//如果是，追加显示
{
String temp = jtf.getText();
jtf.setText(temp + comm);
}else  //如果不是，显示该字符并将追加设置为true
{
jtf.setText(comm);
append = true;
}
}
else if(comm.equals("."))//输入小数点时
{
String temp = jtf.getText();
if(temp.indexOf(".")== -1 && append){//当输入的文本中没有小数点时
jtf.setText(temp+comm);
append = true; //输入小数点后继续追加
}else if(!append){ //当字符串开始时候先输入 " . " 则直接输出" 0. "
jtf.setText("0"+comm);
append = true;
}
}else if("+-*/".indexOf(comm)!= -1)//输入加减乘除符号时，
{//以下运算应该注意数据类型，尤其是大数字和浮点数及int数在运算中的区别
operator = comm;
s1 = jtf.getText();
double d3 = Double.parseDouble(s1);
double d4 = Double.parseDouble(ss);
BigDecimal bd3 = new BigDecimal(d3+"");
BigDecimal bd4 = new BigDecimal(d4+"");
if(operator.equals("+"))//加法时
{
d3 = bd3.add(bd4).doubleValue();
ss = d3+"";
jtf.setText(ss);
}else if(operator.equals("-"))//减法时
{
if(d4 == 0.0){
ss = s1;
jtf.setText(ss);
}else{
d3 = bd4.subtract(bd3).doubleValue();
ss = d3+"";
jtf.setText(ss);
}
}else if(operator.equals("*"))//乘法时
{
if(d4 == 0.0){
ss = s1;
jtf.setText(ss);
}else
{
d3 = bd3.multiply(bd4).doubleValue();
ss = d3+"";
jtf.setText(ss);
}
}else if(operator.equals("/"))//除法时
{
if(d4 == 0.0)
{
ss = s1;
jtf.setText(s1);
}else
{
d3 = bd4.divide(bd3,15,BigDecimal.ROUND_HALF_UP).doubleValue();
}
ss = d3+"";
jtf.setText(ss);
}
append = false; //不继续追加
}else if(comm.equals("="))//输入等号时，计算加减乘除的结果
{
String s2 = jtf.getText();
double d1 = Double.parseDouble(ss);
double d2 = Double.parseDouble(s2);
BigDecimal bd1 = new BigDecimal(d1+"");
BigDecimal bd2 = new BigDecimal(d2+"");
if(operator.equals("+"))
{
d1 = bd1.add(bd2).doubleValue();
}else if(operator.equals("-"))
{
d1 = bd1.subtract(bd2).doubleValue();
}else if(operator.equals("*"))
{
d1 = bd1.multiply(bd2).doubleValue();
}else if(operator.equals("/"))//精确计算浮点除法
{
if(d2!=0.0)
{
d1 = bd1.divide(bd2,15,BigDecimal.ROUND_HALF_UP).doubleValue();
}
}
ss = "0";
jtf.setText(d1+"");
append = false; //不继续追加
}else if(comm.equals("CE")||comm.equals("C"))//输入CE或C时
{
jtf.setText("0");
ss = "0";
append = false;
}else if(comm.equals("+/-"))//改变数值的正负号
{
String temp = jtf.getText();
if(!append)
{
jtf.setText("-");
append = true;
}else if(temp.startsWith("-"))//如果字符串以负号开头
{
jtf.setText(temp.substring(1));
}else
{
jtf.setText("-" + temp);
}
}else if(comm.equals("Backspace"))//输入Backspace时，退回一个字符
{
String temp = jtf.getText();
if(temp.length()>0)
jtf.setText(temp.substring(0,temp.length()-1));
}
}
//主方法
public static void main(String[] args)
{
//创建名为Calculator的计算器对象
new Calculater("Calculater");
}
}
import java.awt.*;
import java.awt.event.*;
import java.math.BigDecimal;
import javax.swing.*;//创建计算器Calculator类，实现ActionListener接口
public class Calculater implements ActionListener
{
//定义变量和按钮数组
private String[] names = {"Backspace","CE","C","+","7","8","9","-",
"4","5","6","*","1","2","3","/","0","+/-",".","="};
private JButton[] buttonArray = new JButton[names.length];
private boolean append = false;//默认追加为false
private String operator = "+";//默认运算符为“+”
private String s1 = "0";//默认字符为0
private String ss = "0";//默认字符为0
//创建可以显示20个字符的文本框
JTextField jtf = new JTextField(20);

//构造方法
public Calculater() {}
public Calculater(String title)
{
//创建窗口、面板，并设置面板布局为网格布局
JFrame jf = new JFrame(title);
JPanel jp = new JPanel();
jp.setLayout(new GridLayout(5,4));
//依次添加按钮到面板中，并为按钮注册监听器
for (int i = 0; i < buttonArray.length; i++)
{
buttonArray[i] = new JButton(names[i]);
buttonArray[i].addActionListener(this);
jp.add(buttonArray[i]);
}
//添加文本框到窗体中
jf.add(jtf,BorderLayout.NORTH);
jf.add(jp);//添加面板到窗体中
jtf.setHorizontalAlignment(JTextField.RIGHT);//设置文本框的水平方向为右
jtf.setText("0");//设置初始文本为0
jtf.setEditable(false);//设置文本框为不可编辑状态
//设置窗体属性
jf.pack();//系统自动设置大小和位置
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

//实现监听接口的actionPerformed方法
public void actionPerformed(ActionEvent e)
{
String comm = e.getActionCommand();
if(comm.matches("\\d")) //用正则表达式判断输出的是否是0~9
{
if(append)//如果是，追加显示
{
String temp = jtf.getText();
jtf.setText(temp + comm);
}else  //如果不是，显示该字符并将追加设置为true
{
jtf.setText(comm);
append = true;
}
}
else if(comm.equals("."))//输入小数点时
{
String temp = jtf.getText();
if(temp.indexOf(".")== -1 && append){//当输入的文本中没有小数点时
jtf.setText(temp+comm);
append = true; //输入小数点后继续追加
}else if(!append){ //当字符串开始时候先输入 " . " 则直接输出" 0. "
jtf.setText("0"+comm);
append = true;
}
}else if("+-*/".indexOf(comm)!= -1)//输入加减乘除符号时，
{//以下运算应该注意数据类型，尤其是大数字和浮点数及int数在运算中的区别
operator = comm;
s1 = jtf.getText();
double d3 = Double.parseDouble(s1);
double d4 = Double.parseDouble(ss);
BigDecimal bd3 = new BigDecimal(d3+"");
BigDecimal bd4 = new BigDecimal(d4+"");
if(operator.equals("+"))//加法时
{
d3 = bd3.add(bd4).doubleValue();
ss = d3+"";
jtf.setText(ss);
}else if(operator.equals("-"))//减法时
{
if(d4 == 0.0){
ss = s1;
jtf.setText(ss);
}else{
d3 = bd4.subtract(bd3).doubleValue();
ss = d3+"";
jtf.setText(ss);
}
}else if(operator.equals("*"))//乘法时
{
if(d4 == 0.0){
ss = s1;
jtf.setText(ss);
}else
{
d3 = bd3.multiply(bd4).doubleValue();
ss = d3+"";
jtf.setText(ss);
}
}else if(operator.equals("/"))//除法时
{
if(d4 == 0.0)
{
ss = s1;
jtf.setText(s1);
}else
{
d3 = bd4.divide(bd3,15,BigDecimal.ROUND_HALF_UP).doubleValue();
}
ss = d3+"";
jtf.setText(ss);
}
append = false; //不继续追加
}else if(comm.equals("="))//输入等号时，计算加减乘除的结果
{
String s2 = jtf.getText();
double d1 = Double.parseDouble(ss);
double d2 = Double.parseDouble(s2);
BigDecimal bd1 = new BigDecimal(d1+"");
BigDecimal bd2 = new BigDecimal(d2+"");
if(operator.equals("+"))
{
d1 = bd1.add(bd2).doubleValue();
}else if(operator.equals("-"))
{
d1 = bd1.subtract(bd2).doubleValue();
}else if(operator.equals("*"))
{
d1 = bd1.multiply(bd2).doubleValue();
}else if(operator.equals("/"))//精确计算浮点除法
{
if(d2!=0.0)
{
d1 = bd1.divide(bd2,15,BigDecimal.ROUND_HALF_UP).doubleValue();
}
}
ss = "0";
jtf.setText(d1+"");
append = false; //不继续追加
}else if(comm.equals("CE")||comm.equals("C"))//输入CE或C时
{
jtf.setText("0");
ss = "0";
append = false;
}else if(comm.equals("+/-"))//改变数值的正负号
{
String temp = jtf.getText();
if(!append)
{
jtf.setText("-");
append = true;
}else if(temp.startsWith("-"))//如果字符串以负号开头
{
jtf.setText(temp.substring(1));
}else
{
jtf.setText("-" + temp);
}
}else if(comm.equals("Backspace"))//输入Backspace时，退回一个字符
{
String temp = jtf.getText();
if(temp.length()>0)
jtf.setText(temp.substring(0,temp.length()-1));
}
}
//主方法
public static void main(String[] args)
{
//创建名为Calculator的计算器对象
new Calculater("Calculater");
}
}

Answer 13

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class OperationButton extends JButton{
   String operateSign;
   public OperationButton(String s){
      super(s);
      operateSign=s;
      setForeground(Color.red);
   }
   public String getOperateSign(){
      return operateSign;
   }
}