What is deques

Answer 1

Deque is an interface defined in java.util package which provides the implementation of Double Ended Queue in Data Structures.
LinkedList is a subclass of Deque which can be used by the programmers to achieve the sequential data structure with FIFO behavior.

Answer 2

double ended queue is data structure.
in queue you can insert from end and delete from starting but double ended queue allows you to handle both deletion and insertion from both side.