Java代码实现计算器加减乘除简易功能

package test;

import javax.swing.;

import java.awt.;

import java.awt.event.KeyAdapter;

import java.awt.event.KeyEvent;

import java.util.HashMap;

import java.util.Stack;

/**

Created by zxx on 2020/10/15.

*/

public class Calculator extends JFrame{

private Stack operandStack= new Stack<>();

private Stack operatorStack = new Stack<>();

private Calculator(){

 setTitle("计算器");

 setSize(266,340);

 //setSize(400,540);

 Container c=getContentPane();

 c.setLayout(null);

 JTextArea jt=new JTextArea(100,100);

 jt.setFont(new Font("Aria",Font.BOLD,32));

 jt.setLineWrap(true);

 JScrollPane sp=new JScrollPane(jt);

 jt.setCaretPosition(jt.getDocument().getLength());

 sp.setBounds(0,0,250,100);

 c.add(sp);

 JPanel p=new JPanel();

 p.setLayout(new GridLayout(5,4,0,0));

 p.setBounds(0,100,250,200);

 String[] num={"(",")","AC","/","7","8","9","*","4","5","6","-","1","2","3","+","0",".","DEL","="};

 JButton[] jb=new JButton[20];

 for(int i=0;i<20;i ++ ){

     jb[i]=new JButton(num[i]);

     p.add(jb[i]);

 }

 c.add(p);

 for(int i=0;i<18;i  ++){

     if(i!=2){

         final int j=i;

         jb[i].addActionListener(e-> jt.append(num[j]));

     }

 }

 jb[2].addActionListener(e->{

     jt.setText("");

     operandStack.clear();

     operatorStack.clear();

 });

 jb[18].addActionListener(e->{

     try{

         jt.setText(jt.getText().substring(0,jt.getText().length()-1));

     }catch(Exception ignored) { }//忽略这个异常   IDEA就是好用！！！

 });

 jb[19].addActionListener(e->{

     try{

         double x= calculate(jt.getText()+ "#");

         jt.setText("");

         jt.append(String.valueOf(x));

     }catch(Exception ex){

         if(ex.getMessage()==null)

             jt.setText("ERROR!");

         else

             jt.setText(ex.getMessage());

     }

 });

 //禁止文本域的enter换行

 KeyStroke enter = KeyStroke.getKeyStroke("ENTER");

 jt.getInputMap().put(enter, "none");

 this.getRootPane().setDefaultButton(jb[19]);

 c.addKeyListener(new KeyAdapter() {

     @Override

     public void keyTyped(KeyEvent e)

     {

     }

     public void keyPressed(KeyEvent e)			//键盘按键监听

     {

     	char label=e.getKeyChar();

     	String k=String.valueOf(label);

     	if(label==KeyEvent.VK_ENTER)

     	{

     		calculate();

     	}

     	else if(label==KeyEvent.VK_BACK_SPACE)

     	{

     		String s = jt.getText();

     		if(s!=null)

     		{

     			calculate();				//调用定义的处理←方法

     		}else

     		{

     			jt.setText(s);

     		}

     	}

     	else

     	{

     		calculate(k);					//按下数字和运算符号的叠加

     	}

     }

     public void keyReleased(KeyEvent e)

     {

     }

 });

 setVisible(true);

 setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

}

private void calculate(){

String b = operatorStack.pop();

double c = operandStack.pop();

double d = operandStack.pop();

double e;

if (b.equals("+")) {

e = d + c;

operandStack.push(e);

}

if (b.equals("-")) {

e = d - c;

operandStack.push(e);

}

if (b.equals("*")) {

e = d * c;

operandStack.push(e);

}

if (b.equals("/")) {

if(c==0)

throw new ArithmeticException("DivideByZero!");//不可修改为Exception

// Exception的异常是必须处理的,是受控异常;而ArithmeticException 不是必须处理的 ,受控异常必须强制处理

e = d / c;

operandStack.push(e);

}

}

private Double calculate(String text){

HashMap<String,Integer> precede=new HashMap<>();

precede.put("(",0);

precede.put(")",0);

precede.put("/",2);

precede.put("*",2);

precede.put("-",1);

precede.put("+",1);

precede.put("#",0);

 operatorStack.push("#");

 int flag=0;

 for(int i=0;i<text.length();i++  ){

     String a=String.valueOf(text.charAt(i));

     if(!a.matches("[0-9.]")){

         if(flag!=i)

             operandStack.push(Double.parseDouble(text.substring(flag,i)));

         flag=i+ 1;

         while(!(a.equals("#")&&operatorStack.peek().equals("#"))){

             if(precede.get(a)>precede.get(operatorStack.peek())||a.equals("(")){

                 operatorStack.push(a);

                 break;

             }else {

                 if(a.equals(")")) {

                     while(!operatorStack.peek().equals("("))

                         calculate();

                     operatorStack.pop();

                     break;

                 }

                 calculate();

             }

         }

     }

 }

 return(operandStack.pop());

}

public static void main(String[] args){

new Calculator();

}

}

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Java代码实现计算器加减乘除简易功能

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