//效率取随机不重复数

     public int[] takeRandom(int num) {

         Random rd = new Random();

         int[] rds = new int[num];//随机数数组

         List list = new ArrayList();//存放有序数字集合

         int index = 0;//随机索引

         for (int i = 0; i < num; i++) {

             list.add(i);

         }

         for (int i = 0; i < num; i++) {

             index = rd.nextInt(num - i);

             rds[i] = (Integer) list.get(index);

             list.remove(index);

         }

         return rds;

     }