Java实现一个简易计算器

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        //计算器界面
        calInter();
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入功能选项：");
        int i = sc.nextInt();
        int j = 1;
        while(true){
            switch (i){
                case 1:
                    System.out.println("结果为："+addInt());
                    break;
                case 2:
                    System.out.println("结果为："+addDouble());
                    break;
                case 3:
                    System.out.println("结果为："+factor());
                    break;
                case 4:
                    System.out.println("结果为："+power());
                    break;
                case 5:
                    exit();
                    j = 0;
                    break;
                default:
                    System.out.println("输入功能选项有误，您只能选择1~5之间的整数，请重新输入！");
            }
            if(j == 0){
                break;
            }
            System.out.println("请输入功能选项：");
            i = sc.nextInt();
        }
    }
    //计算器界面
    public static void calInter(){
        System.out.println("====== 欢迎使用计算器系统 ========");
        System.out.println("1. int + int");
        System.out.println("2. double + double ");
        System.out.println("3. 计算 n 的阶乘");
        System.out.println("4. 计算 a的 n次方");
        System.out.println("5. 退出系统");
    }
    //Int加法
    public static int addInt(){
        Scanner sc = new Scanner(System.in);
        System.out.println("第一个int数为：");
        int a = sc.nextInt();
        System.out.println("第二个int数为：");
        int b = sc.nextInt();
        return a + b;
    }
    //double加法
    public static double addDouble(){
        Scanner sc = new Scanner(System.in);
        System.out.println("第一个double数为：");
        double a = sc.nextDouble();
        System.out.println("第二个数double为：");
        double b = sc.nextDouble();
        return a + b;
    }
    //n的阶乘
    public static int factor(){
        Scanner sc = new Scanner(System.in);
        System.out.println("阶乘n为：");
        int n = sc.nextInt();
        int fact = 1;
        for(int i = 1; i