JAVA.12

import java.util.Random;
import java.util.Scanner;

public class Y1 {

	public static void main(String[] args) {
		Mainmenu();

	}

		 public static void Mainmenu() {
		        Scanner input = new Scanner(System.in);
		        System.out.println("1.登录");
		        System.out.println("2.注册");
		        System.out.println("3.幸运抽奖");
		        System.out.println("4.看小故事");
		        System.out.println("5.退出系统");
		        System.out.println("请选择");
		        int n = input.nextInt();
		        switch (n) {
		        case 1:
		            login();
		            break;
		        case 2:
		            zc();
		            break;
		        case 3:
		            cj();
		            break;
		        case 4:
		            story();
		            break;
		        case 5:
		            tc();
		            break;

		        }
		    }

		    public static void tc() {
		        System.out.println("谢谢使用");

		    }

		    public static void story() {
		        Scanner input = new Scanner(System.in);
		        System.out.println("请选择想看的故事");
		        System.out.println("1.龟兔赛跑");
		        System.out.println("2.农夫与蛇");
		        System.out.println("3.狼来了");
		        int a = input.nextInt();
		        switch (a) {
		        case 1:
		            System.out.println("兔乌赛跑，龟到终点。");
		            break;
		        case 2:
		            System.out.println("农夫救蛇，不知回报。");
		            break;
		        case 3:
		            System.out.println("狼来了。");

		            break;

		        }
		        returnMain();
		    }

		    private static void cj() {
		        Scanner input = new Scanner(System.in);
		        System.out.println("请输入四位会员卡号");
		        int x = input.nextInt();
		        Random r = new Random();
		        int a = r.nextInt(10);
		        if (x / 100 % 10 == a) {
		            System.out.println("恭喜你中奖啦!");
		        } else {
		            System.out.println("谢谢参与");
		        }
		        returnMain();
		    }

		    private static void zc() {
		        Scanner input = new Scanner(System.in);
		        System.out.println("请输入用户名");
		        String name = input.next();
		        System.out.println("请输入密码");
		        String mima = input.next();
		        System.out.println("注册成功");
		        returnMain();
		    }

		    private static void login() {
		        Scanner input = new Scanner(System.in);
		        System.out.println("输入用户名");
		        String uname = input.next();
		        System.out.println("输入密码");
		        String upwd = input.next();
		        if (uname.equals("zs") && upwd.equals("123")) {
		            System.out.println("登录成功");
		        } else {
		            System.out.println("登录失败");
		        }
		        returnMain();
		    }

		    public static void returnMain() {
		        System.out.println("是否返回主菜单?Y/N");
		        Scanner input = new Scanner(System.in);
		        if (input.next().equalsIgnoreCase("Y")) {
		            Mainmenu();
		        } else {
		            System.out.println("谢谢使用");
		        }
		    }

		}

2.编写一个方法，求整数n的阶乘，例如5的阶乘是1*2*3*4*5。

public classY1 {
    public static int jc(int a) {
        int x = 1;
        for (int i = 1; i 

3.编写一个方法，判断该年份是平年还是闰年。
public class Y1 {
    public static void main(String[] args) {
        prn(2018);
    }

    public static void prn(int year) {
        if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
            System.out.println(year + "年是闰年");
        } else {
            System.out.println(year + "年不是闰年");
        }

    }