实例：计算器

package com;

import java.util.Scanner;

public class 计算器 {
    public static void main(String[] args) {
        Scanner ma= new Scanner(System.in);

        for(int i = 0;true;i++) {
            System.out.println("请选择运算方式");
            String z = ma.next();

            switch (z) {
                case "+":
                    System.out.println("当前进行的是加法运算!");
                    System.out.println("请输入a");
                    int a = ma.nextInt();
                    System.out.println("请输入b");
                    int b = ma.nextInt();
                    System.out.println(a + "+" + b +"="+ String.valueOf(a + b));
                    i = 0;
                    break;
                case "-":
                    System.out.println("当前进行的是减法运算!");
                    System.out.println("请输入a");
                    int c = ma.nextInt();
                    System.out.println("请输入b");
                    int d = ma.nextInt();
                    System.out.println(c + "-" + d + '=' + (c - d));
                    i = 0;
                    break;
                case "*":
                    System.out.println("当前进行的是乘法运算!");
                    System.out.println("请输入a");
                    int e = ma.nextInt();
                    System.out.println("请输入b");
                    int f = ma.nextInt();
                    System.out.println(e + "*" + f +"="+ (e * f));
                    i = 0;
                    break;
                case "/":
                    System.out.println("当前进行的是除法运算!");
                    System.out.println("请输入a");
                    int g = ma.nextInt();
                    System.out.println("请输入b");
                    int h = ma.nextInt();
                    System.out.println(g + "/" + h +"="+ (g / h));
                    i = 0;
                    break;
                default:
                    System.out.println("输入违规！请重新输入");
                    break;
            }
        }

    }
}