java实现简易计算器

Java简易计算器

用java语言写的一个简易计算器，实现了最基本的+、-、*、/ 运算。

先来看下效果：

界面简述：
整个面板的由一个JTextFiled组件+16个JButton组件构成，外加一个JPanel组件存放16个按钮，其布局为4x4的网格布局（GridLayout）。

显示框与按钮面板放在了整个面板容器中，布局为BorderLayout，显示框放容器北部，整个按钮面板放容器中部。

功能实现简述：
由匿名内部类实现ActionListener接口，按钮注册进行监听，并捕获按钮事件。
由于该计算器只能计算中缀表达式，即数字与运算符交替出现的表达式，获取输入的运算表达式，并将其存与一个字符串中。

这里需要借助栈来完成表达式的计算，首先将字符串分割成字符串数组，由中缀的定义知数组奇数位为运算符（从第0位开始），偶数位为操作数，因此可将偶数为操作数进栈，遇见+(-)运算符，则将下一个数以正(负）的形式压人栈中，遇见*或/运算符，则将栈顶元素出栈与数组后一元素进行计算，并将其结果重新压入栈中，直至遍历至数组最后一个元素。
最后将栈中的元素进行求和。

 

代码实现：

//package com.cal;
 
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;
import javax.swing.*;
 
class MyException extends Exception{
    public MyException() {
        super();
    }
    public MyException(String message) {
        super(message);
    }
}
 
 class SwingConsole{
    public static void run(final JFrame f,final int width,final int height){
        SwingUtilities.invokeLater(new Runnable(){
            public void run(){
                f.setTitle(f.getClass().getSimpleName());
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setSize(width,height);
                f.setVisible(true);
            }
        });
    }
}
 
public class MyCalculator extends JFrame{
    /*
     * 
     */
 
    private JTextField textField;                //输入文本框
    private String input;                        //结果
    private String operator;                    //操作符
        
    public MyCalculator() {
        input = "";
        operator = "";
        
        Container container = this.getContentPane();
        JPanel panel = new JPanel();
        textField = new JTextField(30);
        textField.setEditable(false);                        //文本框禁止编辑
        textField.setHorizontalAlignment(JTextField.LEFT);
        //textField.setBounds(100, 100, 20, 20);            //在容器布局为空情况下生效
        textField.setPreferredSize(new Dimension(200,30));
        container.add(textField, BorderLayout.NORTH);
        
        String[] name= {"7","8","9","+","4","5","6","-","1","2","3","*","0","C","=","/"};
        
        panel.setLayout(new GridLayout(4,4,1,1));
        
        for(int i=0;i<name.length;i++) {
            JButton button = new JButton(name[i]);
            button.addActionListener(new MyActionListener());
            panel.add(button);
        }
        container.add(panel,BorderLayout.CENTER);
    }
    
    class MyActionListener implements ActionListener{            //内部类实现按钮响应
 
        @Override
        public void actionPerformed(ActionEvent e) {
            int cnt=0;
            String actionCommand = e.getActionCommand();            //获取按钮上的字符串
            if(actionCommand.equals("+") || actionCommand.equals("-") || actionCommand.equals("*")
                    || actionCommand.equals("/")) {
                input += " " + actionCommand + " ";
            }
            else if(actionCommand.equals("C")) {                    //清除输入
                input = "";
            } 
            else if(actionCommand.equals("=")) {                    //按下等号
                try {
                    input+= "="+calculate(input);
                } catch (MyException e1) {
                    if(e1.getMessage().equals("Infinity"))
                        input+= "=" + e1.getMessage();
                    else
                        input = e1.getMessage();
                }
                textField.setText(input);
                input="";
                cnt = 1;
            }
            else
                input += actionCommand;                            //按下数字
            
            if(cnt == 0)
                textField.setText(input);
        }
    }
    
    private String calculate(String input) throws MyException{                //计算函数
        String[] comput = input.split(" ");                    
        Stack<Double> stack = new Stack<>();
        Double m = Double.parseDouble(comput[0]);
        stack.push(m);                                        //第一个操作数入栈
        
        for(int i = 1; i < comput.length; i++) {
            if(i%2==1) {                
                if(comput[i].equals("+"))
                    stack.push(Double.parseDouble(comput[i+1]));
                if(comput[i].equals("-"))
                    stack.push(-Double.parseDouble(comput[i+1]));
                if(comput[i].equals("*")) {                    //将前一个数出栈做乘法再入栈
                    Double d = stack.peek();                //取栈顶元素
                    stack.pop();
                    stack.push(d*Double.parseDouble(comput[i+1]));
                }
                if(comput[i].equals("/")) {                    //将前一个数出栈做乘法再入栈
                     double help = Double.parseDouble(comput[i+1]);  
                     if(help == 0)
                         throw new MyException("Infinity");            //不会继续执行该函数
                     double d = stack.peek(); 
                     stack.pop(); 
                     stack.push(d/help);  
                }
            }
        }
        
        double d = 0d;
        
        while(!stack.isEmpty()) {            //求和
            d += stack.peek();
            stack.pop();
        }
        
        String result = String.valueOf(d);
        return result;
    }
 
    public static void main(String[] args) {
        SwingConsole.run(new MyCalculator(), 250, 300);
    }
}

 一、先实现窗口

package 菜鸟教程.NumberMath;

//package com.cal;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;
import javax.swing.*;



class SwingConsole{
    public static void run(final JFrame f,final int width,final int height){
        SwingUtilities.invokeLater(new Runnable(){//线程里修改swing组件的外观
            public void run(){
                f.setTitle(f.getClass().getSimpleName());
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setSize(width,height);
                f.setVisible(true);
            }
        });
    }
}

public class MyCalculator extends JFrame{


    public static void main(String[] args) {
        SwingConsole.run(new MyCalculator(), 250, 300);
    }
}

 二、实现其他按钮和输入框等

package 菜鸟教程.NumberMath;

//package com.cal;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;
import javax.swing.*;



class SwingConsole{
    public static void run(final JFrame f,final int width,final int height){
        SwingUtilities.invokeLater(new Runnable(){//线程里修改swing组件的外观
            public void run(){
                f.setTitle(f.getClass().getSimpleName());
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setSize(width,height);
                f.setVisible(true);
            }
        });
    }
}

public class MyCalculator extends JFrame{

    private JTextField textField;                //输入文本框
    private String input;                        //结果
    private String operator;                    //操作符

    public MyCalculator() {
        input = "";
        operator = "";

        Container container = this.getContentPane();
        JPanel panel = new JPanel();
        textField = new JTextField(30);
        textField.setEditable(false);                        //文本框禁止编辑
        textField.setHorizontalAlignment(JTextField.LEFT);
        //textField.setBounds(100, 100, 20, 20);            //在容器布局为空情况下生效
        textField.setPreferredSize(new Dimension(200,30));
        container.add(textField, BorderLayout.NORTH);

        String[] name= {"7","8","9","+","4","5","6","-","1","2","3","*","0","C","=","/"};

        panel.setLayout(new GridLayout(4,4,1,1));

        for(int i=0;i<name.length;i++) {
            JButton button = new JButton(name[i]);
//            button.addActionListener(new MyActionListener());
            panel.add(button);
        }
        container.add(panel,BorderLayout.CENTER);
    }


    public static void main(String[] args) {
        SwingConsole.run(new MyCalculator(), 250, 300);
    }
}