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();  
}  

}