offerLast

offerLast is a method in the Deque interface of the Java collections framework that inserts a given element at the tail (end) of the deque. It returns a boolean to indicate whether the insertion succeeded.

The signature is boolean offerLast(E e). The method attempts to add the element at the end and returns true if successful. If the deque has a bounded capacity and cannot accept more elements at this time, offerLast returns false rather than throwing an exception. This behavior contrasts with addLast, which may throw an IllegalStateException when space is not available.

Implementation details vary by concrete class. In unbounded deques such as LinkedList or ArrayDeque, offerLast typically always succeeds (subject to element nullability rules of the implementation) and thus returns true. In bounded or blocking deques, such as LinkedBlockingDeque, offerLast can return false when the deque is full, or it may interact with other concurrency controls in blocking variants.

Null element handling also depends on the specific implementation. Some deque implementations permit null elements, while others do not and may throw a NullPointerException if a null is supplied.

offerLast is part of a family of methods for manipulating a deque from either end, including offerFirst (insert at the head), addLast (insert at the tail with potential exception), and remove or poll operations at both ends. The choice between offerLast and addLast depends on whether the calling code needs a non-throwing failure mode or a throwing exception to signal capacity problems.

In summary, offerLast provides a non-throwing way to append an element to the end of a deque, returning true on success and false if space constraints prevent insertion.