Java ConcurrentLinkedDeque.addFirst() is a method in the Java ConcurrentLinkedDeque class that inserts an element at the front of the deque. It is a thread-safe operation that ensures efficient concurrent access in multi-threaded environments. Introduced in Java 2004 with Java 5, addFirst() is used in concurrent applications where elements need to be added to the front of the deque, such as in task scheduling or event handling.

https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html