ArrayBlockingQueue [1] uses a ring buffer backed by a fixed-size array, too. It is really hard to say where the speed-up comes from without seeing the code, but

ArrayBlockingQueue [1] uses a ring buffer backed by a fixed-size array, too. It is really hard to say where the speed-up comes from without seeing the code, but it is certainly not from using a ring buffer because both of the compared implementations do so. I guess they just were more careful when they designed the auxiliary state and the operation on it, for example ArrayBlockingQueue explicitly tracks the number of elements in the queue with a separate field - instead of deriving it from the insert and remove pointers - and therefore this field is contented by readers and writers. Also preallocating entries for all slots to work around Java's lack of support for arrays of value types certainly removes some overhead from the allocator. EDIT: Just realized that the code is on GitHub - will have a look. [1] http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/concurrent/ArrayBlockingQueue.java http://grepcode.com/file/repository.grepcode.com/java/root/j...