Java第九次作业

1.编写一个方法，实现冒泡排序（由小到大），并调用该方法

 public static void main(String[] args) {
        // TODO Auto-generated method stub
         int []a={200,98,300,98};
            mp(a);
            for (int i = 0; i < a.length; i++) {
                System.out.println(a[i]);
            }
    }
        public static void mp(int[]b){
            for (int i = 0; i < b.length - 1; i++) {
                for (int j = 0; j < b.length - 1 - i; j++) {
                    if (b[j] > b[j + 1]) {
                        int temp = b[j];
                        b[j] = b[j + 1];
                        b[j + 1] = temp;
                    }
                }
            }
        }

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。 [必做题]

 public static void main(String[] args) {
        // TODO Auto-generated method stub
        int sum1=jc(5);
        System.out.println(sum1);
    }
    public static int jc(int n){
        int sum=1;
        for (int i =1; i <=n; i++) {
            sum*=i;
        }
        return sum;
    }

3.编写一个方法，判断该年份是平年还是闰年。[必做题]

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

    public static void nian() {
        Scanner input = new Scanner(System.in);
        System.out.println("输入年份");
        int year = input.nextInt();
        if (year % 4 == 0 && year % 100 != 100 || year % 400 == 0) {
            System.out.println("该年份为闰年");
        } else {
            System.out.println("该年份是平年");
        }
    }

4.课堂没完成的menu菜单，实现幸运抽奖功能

import java.util.Random;
import java.util.Scanner;
public class gc4 {
    public static void mainMenu(){
        Scanner input=new Scanner(System.in);
        System.out.println("欢迎使用本系统");
        System.out.println("1.登录");
        System.out.println("2.注册");
        System.out.println("3.幸运抽奖");
        System.out.println("4.退出");
        System.out.println("请选择");
        int i=input.nextInt();
        switch(i){
        case 1:
            login();
            break;
        case 2:
            reg();
            break;
        case 3:
            lucky();    
        }    
    }
    private static void lucky() {
        // 输入四位会员卡号，如果百位数等于随机数，幸运会员。否则不是。同时也要询问是否返回主菜单
        Random r=new Random();
        int a=r.nextInt();
        Scanner input =new Scanner(System.in);
        System.out.println("请输入4位会员卡号");
        int b=input.nextInt();
        int c=b%1000/100;
        if (c==a) {
            System.out.println("是幸运会员");
        }
        else{
            System.out.println("不是幸运会员");
            returnMain();
        }
            }
    public static void returnMain(){
        Scanner input=new Scanner(System.in);
        System.out.println("是否返回主菜单？");
        if(input.next().equalsIgnoreCase("Y"))
            mainMenu();
        else
            System.out.println("谢谢使用");
    }
    
    public static void reg() {
        // TODO Auto-generated method stub
        Scanner input=new Scanner(System.in);
        System.out.println("输入要注册的用户名");
        String uname=input.next();
        System.out.println("输入注册密码");
        String upwd=input.next();
        System.out.println("注册成功");
        returnMain();
        
        
    }

    public 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("ok");
        }else{
            System.out.println("fail");
        }
        returnMain();        
    }
    public static void main(String[] args) {
        mainMenu();
    }