pollFirst

pollFirst is a method in the Java standard library’s Deque interface. It retrieves and removes the first element of the deque, or returns null if the deque is empty. The operation is non-blocking and does not throw an exception when the deque is empty.

In terms of behavior, pollFirst returns the element at the front of the deque and removes it. If the deque has no elements, it returns null. This differs from removeFirst, which also removes the first element but throws a NoSuchElementException if the deque is empty. The method is typically implemented with constant time complexity (O(1)) in common deque implementations such as ArrayDeque and LinkedList.

pollFirst is effectively the Deque-specific equivalent of poll() when used through the Deque interface, both of which remove and return the head of the deque. There is a complementary pollLast() method that removes and returns the last element, or null if empty. For blocking variants, the BlockingDeque interface provides takeFirst() and related methods that block until an element becomes available.

Common usage involves non-blocking queue operations in single- or multi-threaded contexts. For example, a producer-consumer setup may use pollFirst() to fetch the next task from the front of a shared deque without risking an exception if the deque is temporarily empty. pollFirst is available in many deque implementations, such as ArrayDeque, LinkedList, and ConcurrentLinkedDeque, and is part of the standard Java collections framework since Java 6.