The java.util.Queue interface defines the queue data structure, which stores elements in the order in which they are inserted. New additions go to the end of the line, and elements are removed from the front. It creates a first-in first-out system. This interface is implemented by java.util.LinkedList, java.util.ArrayDeque, and java.util.PriorityQueue. LinkedList, of course, also implements the List interface and can also be used as one. But it also has the Queue methods. ArrayDeque implements the queue as an array. Both LinkedList and ArrayDeque also implement the java.util.Deque interface, giving it more flexibility.