java第十次作业

1.编写一个方法，实现冒泡排序（由小到大），并调用该方法

package sj10;
import java.util.Scanner;
public class jw {
    public static void main(String[]args){
        Scanner input=new Scanner(System.in);
        System.out.println("请输入五个数");
        int a[]=new int [5];
        for (int i = 0; i < a.length; i++) {
            a[i]=input.nextInt();

        } for (int i = 0; i < a.length - 1; i++) {
            for (int j = 0; j < a.length - 1 - i; j++) {
                if (a[j] > a[j + 1]) {
                    int temp = a[j];
                    a[j] = a[j + 1];
                    a[j + 1] = temp;
                }
            }
        }
        System.out.println("排序后为:");
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }
    }
    }

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]

package sj10;
import java.util.Scanner;
public class sj {


        // TODO 自动生成的方法存根
         public static int jc(int a) {
                int sum = 1;
                for (int i = 1; i <= a ; i++) {
                    sum *= i;
                }
                System.out.println(+a+"的阶乘是");
                return sum;
            }

            public static void main(String[] args) {
                System.out.println(jc(5));
            }

    }

3.编写一个方法，判断该年份是平年还是闰年。[必做题]

package sj10;
import java.util.Scanner;
public class sj {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        year();
     }
    public static void year(){
        Scanner input=new Scanner(System.in);
        System.out.println("输入年份");
          int year=input.nextInt();
          if(year%4==0&&year%100!=0||year%400==0){
             System.out.println(year+"是闰年");
             }else{
          System.out.println(year+"是平年");
         }
    }
}

4.课堂没完成的menu菜单，实现幸运抽奖功能

package sj10;
import java.util.Random;
import java.util.Scanner;
public class sj {
    public static void main(String[] args) {
        mainMenu();
    }
     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();

            }

        }

        public static void lucky() {
            Scanner input = new Scanner(System.in);
            System.out.println("输入一个四位数");
            Random r = new Random();
            int x = r.nextInt(10);
            int num = input.nextInt();
            while (num < 1000 || num > 10000) {
                System.out.println("输入有误,重新输入");
                num = input.nextInt();
                if (num >= 1000 && num < 10000) {
                    break;
                }
            }
            int bai = num % 1000 / 100;
            if (bai == x) {
                System.out.println("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("ls") && upwd.equals("123")) {
                System.out.println("ok");
            } else {
                System.out.println("fail");
         }
            returnMain();
    }
}