Collection framework

Queue interface

• Represents utility data structures (like Stack, Queue, ...) data structure.
• Implementations: LinkedList, ArrayDeque, PriorityQueue.
• Can be accessed using iterator, but no random access.

Methods:

• boolean add(E e) - throw IllegalStateException if full.
• E remove() - throw NoSuchElementException if empty
• E element() - throw NoSuchElementException if empty
• boolean offer(E e) - return false if full.
• E poll() - returns null if empty
• E peek() - returns null if empty

In queue, addition and deletion is done from the different ends (rear and front).

Deque interface

• Represents double ended queue data structure i.e. add/delete can be done from both the ends.