java 编程实现简单的计算器

 学习java Swing组件后，就想写一个简单的计算器。在博客记录下，代码都经过测试。

package cn.edu.usst;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingConstants;
import javax.swing.WindowConstants;

public class Calculator extends JFrame implements ActionListener {
    private static final long serialVersionUID = 1L;
    String []arr= {"7","8","9","+","4","5","6","-",
            "1","2","3","*",".","0","=","/"};
    JButton b[]=new JButton[16];
     JTextField jt;
     String input="";//输入的字符串
     public Calculator() {
         Container c=getContentPane();
         JPanel jp1=new JPanel();
         JPanel jp2=new JPanel();
         JPanel jp3=new JPanel();
         JButton b1=new JButton("清零");
          JButton b2=new JButton("退格");
          GridLayout g=new GridLayout(4,4,5,5);
         jp1.setLayout(new BorderLayout());
         jp2.setLayout(g);
        
         jp3.setLayout(new GridLayout(1, 2,5,5));
         
         jt=new JTextField();
         jt.setPreferredSize(new Dimension(150,30));
         jt.setHorizontalAlignment(SwingConstants.LEFT);
         c.add(jp1,BorderLayout.NORTH); 
         jp1.add(jt,BorderLayout.WEST);
         jp1.add(jp3,BorderLayout.EAST);
         jp3.add(b1);
         jp3.add(b2);
         b1.setBackground(Color.gray);
         b2.setBackground(Color.gray);
         b1.addActionListener(this);
         b2.addActionListener(this);
         for(int i=0;i<arr.length;i++) {
             b[i]=new JButton(arr[i]);
             jp2.add(b[i]);
             b[i].addActionListener(this);
         }
        
         c.add(jp2,BorderLayout.CENTER);
         setVisible(true);
         
         setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
         setSize(300, 250);
         setTitle("计算器");
         
         
     }
     @Override
        public void actionPerformed(ActionEvent e) {
        
            // TODO Auto-generated method stub
            int t=0;
            String s=e.getActionCommand();
            if(s.equals("+")||s.equals("-")||s.equals("*")||s.equals("/")) {
                input+=" "+s+" ";      //如果碰到运算符，就在运算符前后分别加一个空格，
                                       //为后面的分解字符串做准备
                
            }else if(s.equals("清零")) {
                input="";
            }else if(s.equals("退格")) {
                if((input.charAt(input.length()-1))==' ') { //检测字符串的最后一个字符是否为空格,
                    input=input.substring(0,input.length()-3);//如果是则删除末尾3个字符，否则删除
                                                              //1个字符 
                }else {
                input=input.substring(0,input.length()-1);
                }
            }
            else if(s.equals("=")) {
                input=compute(input);
                jt.setText(input);
                input="";
                t=1;
            } 
               else  
                    input += s;
                if(t==0) { 
                jt.setText(input);  
                }
     }
    private String compute(String str) {
        // TODO Auto-generated method stub
        String array[];
        array=str.split(" ");
        Stack<Double> s=new Stack<Double>();
        Double a=Double.parseDouble(array[0]);
        s.push(a);
        for(int i=1;i<array.length;i++) {
            if(i%2==1) {
                if(array[i].compareTo("+")==0)    
                {    
                    double b= Double.parseDouble(array[i+1]);    
                    s.push(b);    
                }
                if(array[i].compareTo("-")==0)    
                {    
                    double b= Double.parseDouble(array[i+1]);    
                    s.push(-b);    
                }
                if(array[i].compareTo("*")==0)    
                {    
                    double b= Double.parseDouble(array[i+1]);    
                 
                    double c=s.pop();
                  
                    c*=b;
                    s.push(c);
                    
                    
                }
                if(array[i].compareTo("/")==0)    
                {    
                    double b= Double.parseDouble(array[i+1]);    
                 
                    double c=s.peek();
                    s.pop();
                    c/=b;
                    s.push(c);
                    
                    
                }
            }
        }
        double sum=0;
        while(!s.isEmpty()) {
            sum+=s.pop();
        
        }
        String result=String.valueOf(sum);
        return result;
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
          new Calculator();
    }

    

}

计算器界面如图所示：

测试计算功能：