计算器实现

package com.lei;import java.util.*;public class JiSuan {    /**     * 属性     */    Scanner input = new Scanner(System.in);    double num1;    double num2;        /**     * 方法     */        public double suan() {        double num3 = 0;        System.out.print("请输入序号：1(+)2(-)3(*)4(/)：");        int open = input.nextInt();        switch(open) {        case 1:            num3 = num1+num2;            System.out.println(num1+ "+"+num2+"="+num3);            break;        case 2:            num3 = num1-num2;            System.out.println(num1+ "-"+num2+"="+num3);            break;        case 3:            num3 = num1*num2;            System.out.println(num1+ "*"+num2+"="+num3);            break;        case 4:            num3 = num1/num2;            System.out.println(num1+ "/"+num2+"="+num3);            break;        default:            System.out.println("输入错误");            break;        }        return num3;            }}

package com.lei;import java.util.*;public class JiSuan2 {    public static void main(String[] args) {        JiSuan suan = new JiSuan();        Scanner input = new Scanner(System.in);        do {        System.out.println("请输入第一个数：");        suan.num1 = input.nextDouble();        System.out.println("请输入第二个数：");        suan.num2 = input.nextDouble();        suan.suan();        }while(true);    }}