To generate unique book IDs, you use an AtomicInteger that ensures that the incrementation operation is atomic, and thus thread-safe. 要生成惟一的图书IDs,您将使用一个AtomicInteger,它能确保增量操作是原子级的(atomic),从而确保线程安全。
Post incrementation actually causes in the creation of a temporary var that is then incremented. 后置递增实际上会发生一个暂时变量,这个常设变量随后被递增。