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();
  
  }
  
  }