java第十周作业

1.编写一个方法，实现冒泡排序（由小到大），并调用该方法

package homework;

import java.util.Scanner;

public class tets31 {
	public static void main(String[] args) {
		int[] arr = new int[5];
		System.out.println("输入五个数");
		Scanner sc = new Scanner(System.in);
		for (int i = 0; i < 5; i++) {
			arr[i] = sc.nextInt();
		}
		paixu(arr);
	}

	public static void paixu(int[] arr) {
		for (int i = 0; i < arr.length - 1; i++) {
			for (int j = 0; j < arr.length -1- i; j++) {
				int temp;
				if (arr[i] > arr[i + 1]) {
					temp = arr[i + 1];
					arr[i + 1] = arr[i];
					arr[i] = temp;
				}
			}
		}

		for (int i = 0; i < arr.length; i++) {
			System.out.print(arr[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 homework;

import java.util.Scanner;

public class test32 {
	public static void main(String[] args) {
		System.out.println("输入一个整数");
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println("这个数阶乘是:"+sum(n));
	}
	
	public static int sum(int n) {
		int sum = 0;
		for (int i = 1; i <= n; i++) {
			sum +=i*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]

package homework;

import java.util.Scanner;

public class test33 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("输入一个年份");
		int n = sc.nextInt();
		year(n);

	}

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

　　

4.课堂没完成的menu菜单，实现幸运抽奖功能

package homework;

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

public class test34 {
	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.退出系统");
		System.out.println("请选择：");
		int i = input.nextInt();
		switch (i) {
		case 1:
			login();
			break;
		case 2:
			register();
			break;
		case 3:
			choujiang();
			break;
		}
	}

	public static void register() {
		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 pwd = input.next();
		System.out.println("注册成功");
		returnMain();
	}

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

	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 pwd = input.next();
		if (uname.equals("1") && pwd.equals("1"))
			System.out.println("成功");
		else
			System.out.println("失败");
		returnMain();

	}

	public static void choujiang() {
		Scanner sc = new Scanner(System.in);
		Random r = new Random();
		int a = r.nextInt(10);
		System.out.println("输入四位会员卡号");
		int number = sc.nextInt();
		int b = number % 100 / 10;
		System.out.println("幸运数字为" + a);
		if (b == a) {
			System.out.println("是幸运会员");
		} else {
			System.out.println("不是幸运会员");
		}
		returnMain();
	}

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