Java
Queue & Deque
Master Queue and Deque interfaces for FIFO and double-ended queue operations.
By TechCoder TeamLast updated: 2026-06-02
In a Nutshell
Master Queue and Deque interfaces for FIFO and double-ended queue operations. This hands-on tutorial focuses on practical implementation of queue & deque concepts.
Queue & Deque
Queue Interface
A Queue is a FIFO (First-In-First-Out) data structure.
Common Implementations
- LinkedList - General-purpose queue
- PriorityQueue - Elements ordered by priority
- ArrayDeque - Fast, resizable array-based queue
Key Methods
| Method | Description |
|---|---|
add(e) / offer(e) | Add element to queue |
remove() / poll() | Remove and return head |
element() / peek() | Return head without removing |
Queue<String> queue = new LinkedList<>();
queue.offer("First");
queue.offer("Second");
queue.offer("Third");
System.out.println(queue.poll()); // "First"
System.out.println(queue.peek()); // "Second"
PriorityQueue
Elements are ordered by natural ordering or a custom Comparator.
PriorityQueue<Integer> pq = new PriorityQueue<>();
pq.offer(30);
pq.offer(10);
pq.offer(20);
System.out.println(pq.poll()); // 10 (smallest first)
Deque Interface
A Deque (Double-Ended Queue) allows insertion and removal from both ends.
Common Implementation
- ArrayDeque - Preferred over Stack and LinkedList
Key Methods
| Method | Description |
|---|---|
addFirst(e) / offerFirst(e) | Add to front |
addLast(e) / offerLast(e) | Add to back |
removeFirst() / pollFirst() | Remove from front |
removeLast() / pollLast() | Remove from back |
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Quiz
Quiz
Question 1 of 3What does FIFO stand for?
First-In-First-Out
Fast-In-Fast-Out
First-In-Final-Out