Thread-safety of BlockingQueue's drainTo() method

Question

Documentation of BlockingQueue says bulk operations are not thread-safe, though it doesn\'t explicitly mention the method drainTo().

BlockingQueue imp

Answer 1

drainTo() is thread safe in the sense that any operation on the queue that happens at the same time will not change the result nor will it corrupt the state of the queue. Otherwise, the method would be pretty pointless.

You could run into problems if the target collection (the one to which the results are added) does something "clever". But since you usually drain the queue to a collection to which only a single thread has access, it's more of a theoretical problem.