12、写一个计算器

package com.wzt.www.method;

import java.util.Scanner;

/**
 * @author WZT
 * @create 2021-03-27 8:44
 */
public class Calculator01 {
    
    
    public static void main(String[] args) {
    
    
        while (true) {
    
    
            System.out.println("请输入+、-、*、/中任意一个符号,以回车键结束");
            Scanner scanner = new Scanner(System.in);
            String operator = scanner.next();
            if (operator.equals("exit")) {
    
    
                System.out.println("退出计算器");
                scanner.close();
            } else {
    
    
                System.out.println("请输入需要进行运算的两个数字，每输入一个用回车键结束");
            }
            if (operator.equals("+")||operator.equals("-")||operator.equals("*")||operator.equals("/")) {
    
    
                double d1 = scanner.nextDouble();
                double d2 = scanner.nextDouble();
                double result = 0;
                switch (operator) {
    
    
                    case "+":
                        result = add(d1, d2);
                        break;
                    case "-":
                        result = sub(d1, d2);
                        break;
                    case "*":
                        result = mul(d1, d2);
                        break;
                    case "/":
                        result = div(d1, d2);
                        break;
                }


                System.out.println(d1 + operator + d2 + "=" + result);
                //scanner.close();
            }else {
    
    
                System.out.println("输入不合法");
            }
        }
    }

    public static double add(double x,double y){
    
    
        return x+y;
    }
    public static double sub(double x,double y){
    
    
        return x-y;
    }
    public static double mul(double x,double y){
    
    
        return x*y;
    }
    public static double div(double x,double y){
    
    
        return x/y;
    }

}

• 一定要switch中加入break
• while（true）是循环语句