Android Arraydeque Source

The Deque interface, which is implemented using circular queues, is known as:
-when stack is faster than stack
-When the queue is faster than LinkedList

Iterator is fail fast, save tail location at creation time, next check if tail change, if change is exception.

A full-on bit manipulation
-Find the whole power of the smallest two greater than numelements:

initialCapacity = numElements;            |= (initialCapacity >>>  1);            |= (initialCapacity >>>  2);            |= (initialCapacity >>>  4);            |= (initialCapacity >>>  8);            |= (initialCapacity >>> 16);            initialCapacity++;

-Full power mod for two

mask = size - 1;(h + 1) & mask;

Android Arraydeque Source