Array-Deque

ArrayDeque in Java

Overview

The ArrayDeque class in Java is a part of the java.util package and implements the Deque interface. It provides a resizable array-based implementation of a double-ended queue, allowing elements to be added or removed from both ends efficiently.

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Characteristics of ArrayDeque

Feature	Details
Package	java.util
Allows Duplicates	Yes
Ordering	FIFO (First In, First Out) or LIFO (Last In, First Out) depending on usage
Thread-Safe	No
Initial Capacity	16 (default)

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Key Features of ArrayDeque

• Double-Ended Queue: Allows insertion and removal of elements from both ends of the queue.
• Efficient Operations: All operations (add, remove) are done in constant time (O(1)).
• Resizable Array: The underlying array dynamically grows or shrinks as needed.
• Not Synchronized: Unlike LinkedList, ArrayDeque is not thread-safe.
• No Capacity Limitation: The deque grows as needed, with no fixed size.

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How to Use ArrayDeque

Importing ArrayDeque

import java.util.ArrayDeque;

Creating an ArrayDeque

ArrayDeque<Type> arrayDeque = new ArrayDeque<>();

• Example

  ArrayDeque<Integer> integerDeque = new ArrayDeque<>();
  ArrayDeque<String> stringDeque = new ArrayDeque<>();

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ArrayDeque Specific Methods

The ArrayDeque class provides additional methods beyond those in the Queue and Deque interfaces. Here are some commonly used ones:

Method	Description	Return Type	Example
addFirst()	Inserts the specified element at the front of the deque.	void	arrayDeque.addFirst(10);
addLast()	Inserts the specified element at the end of the deque.	void	arrayDeque.addLast(20);
offerFirst()	Inserts the specified element at the front of the deque, returning true if successful.	boolean	boolean added = arrayDeque.offerFirst(30);
offerLast()	Inserts the specified element at the end of the deque, returning true if successful.	boolean	boolean added = arrayDeque.offerLast(40);
peekFirst()	Retrieves, but does not remove, the first element of the deque, or returns null if empty.	Type	Type first = arrayDeque.peekFirst();
peekLast()	Retrieves, but does not remove, the last element of the deque, or returns null if empty.	Type	Type last = arrayDeque.peekLast();
pollFirst()	Retrieves and removes the first element of the deque, or returns null if empty.	Type	Type first = arrayDeque.pollFirst();
pollLast()	Retrieves and removes the last element of the deque, or returns null if empty.	Type	Type last = arrayDeque.pollLast();
removeFirst()	Removes and returns the first element of the deque.	Type	Type first = arrayDeque.removeFirst();
removeLast()	Removes and returns the last element of the deque.	Type	Type last = arrayDeque.removeLast();

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Example Code

import java.util.ArrayDeque;

public class ArrayDequeExample {
    public static void main(String[] args) {
        // Create an ArrayDeque
        ArrayDeque<Integer> arrayDeque = new ArrayDeque<>();

        // Add elements
        arrayDeque.addFirst(10);
        arrayDeque.addLast(20);
        arrayDeque.addFirst(30);

        // Peek at the first and last elements
        System.out.println("First element: " + arrayDeque.peekFirst());
        System.out.println("Last element: " + arrayDeque.peekLast());

        // Remove elements
        System.out.println("Removed first element: " + arrayDeque.pollFirst());
        System.out.println("Removed last element: " + arrayDeque.pollLast());

        // Display the remaining elements
        System.out.println("Remaining elements: " + arrayDeque);
    }
}

For more: ArrayDequeDataStructure.java