用Math类中的随机函数产生10000个0~999范围的随机数并存于数组。从键盘接收一个0~999的数x，然后用5-8个线程并发查找x的所有下标位置(The random numbers of 10000 0~999 ranges are produced by using random functions in the Math class to coexist in the array. Receive a number of 0~999 from the keyboard, x, and