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 gc;
public class gc {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
int a[]={2,4,6,5,9,8,7};
px(a);
for (int i = 0; i < a.length; i++) {
    System.out.println(a[i]);
}
    }
 
    private static void px(int[] a) {
        // TODO Auto-generated method stub
        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 b=a[j];
                    a[j]=a[j+1];
                    a[j+1]=b;
                }
            }
        }
    }
 
}

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 gc;
public class gc2 {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
int a=5;
System.out.println(b(a));
    }
 
    private static int b(int a) {
        // TODO Auto-generated method stub
        int sum=1;
        for (int j = 1; j <=a; j++) {
            sum*=j;
        }
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 gc;
import java.util.Scanner;
public class gc3 {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
Scanner input =new Scanner(System.in);
System.out.println("请输入一个年份");
year(input.nextInt());
    }
    private static void year(int year) {
        // TODO Auto-generated method stub
        if (year%4==0&&year%100!=0||year%400==0) {
            System.out.println(year+"是闰年");}
            else{
                System.out.println(year+"不是闰年");
            }
        }
    }

4.课堂没完成的menu菜单，实现幸运抽奖功能

package gc;
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();
    }
}