做一个放号器, 多个线程同时申请号码不重复,断电后能恢复. 比如: 线程1 : 1, 4, 5, 6, 8, 9, 14… 线程2 : 2, 3, 7, 10, 11, 12, 13…-The do a sth multiple threads at the same time apply for the number of non-repetition, can be restored after power failure. Example: thread 1: 1, 4,