Java案例:双色球的实现

//随机生成双色球号码

//案例：6颗红球(33选1)  1颗蓝球(16选1)

代码实现如下：

import java.util.Random;
import java.util.Arrays;
//包含Arrays

public class HelloWorld {
	public static void main(String[] args){

		String[] getball = getBalls();
		System.out.println(Arrays.toString(getball));
	}

	public static String[] getBalls()
	{
		//随机生成双色球号码
		//案例：6颗红球(33选1)  1颗蓝球(16选1)
		String []pool = {
		"01","02","03","04","05","06","07","08",
		"09","10","11","12","13","14","15","16",
		"17","18","19","20","21","22","23","24",
		"25","26","27","28","29","30","31","32","33"
		};
		//用一个数组存放6个蓝色的球
		String[] balls = new String[6];
		int length = 0 ;
		//从pool数组中随机选取6个球，放入数组中，并且不能有重复
		/*
		 * 1、如何随机取
		 *    Random r = new Random();
		 *    r.nextInt(n); //取到0到n之间的随机数
		 * 2、如果不重复
		 * 	  一个下标的球被使用我们给它加个标识
		 *   boolean[] flag  = new bootlean[pool.length];数组中元素默认为false
		 */
		boolean[] used = new boolean[pool.length];
		Random r = new Random();
		while(true){
			int index = r.nextInt(pool.length);
			//说明该下标已经被使用过
			if(used[index])
				continue ; //结束本次循环，继续下一次循环
			balls[length++] = pool[index];//把选中的球放入球数组
			used[index] = true ;//把选中的球标识为已经使用过。
			if(length == balls.length) //如果下标等于6，证明选完了
				break ;
		}
		//红色的球已经选完了
		Arrays.sort(balls);
		//扩容一个空间，最后一个放蓝球
		//balls = Arrays.copyOf(balls,balls.length+1); 不知道为什么不行，疑惑中
		String []str = new String[balls.length+1]; //所以我只能使用这种老土的方法来实现数组扩容了
		for(int i = 0 ; i < balls.length ; i++)
			str[i] = balls[i];
		balls = str ;
		//balls = Arrays.copyOf(balls,balls.length+1);
		//蓝色的球16选1即可
		balls[balls.length-1] = pool[r.nextInt(16)];
		return balls ;
	}
}