Stack Java Library

In Java, there are multiple ways to use built-in libraries for Stack.

Stack Class

• It is a legacy collection from early Java versions. It is outdated and rarely used in modern Java
• It's synchronized and thread-safe, which can be slower in single-threaded applications like doing data structures and CP problems.
• Synchronized by default, which might add unnecessary overhead if thread-safety isn't required.

ArrayDeque Class

• Faster performance for single-threaded scenarios.
• Resizable array-backed without the overhead of synchronization.
• More flexible, as it can also be used as a queue.
• Cannot store null elements (throws NullPointerException if attempted).

If you are not sure for a coding problem, you may always use this for fast performance.

import java.util.ArrayDeque;
import java.util.Deque;

public class GFG {

	// Driver Code
	public static void main(String[] args)
	{

		// Creating an ArrayDeque to use
		// as a Stack
		Deque<Integer> s = new ArrayDeque<Integer>();

		// Inserting elements in the Stack
		// using push() operation
		s.push(17);
		s.push(19);
		s.push(15);

		// Printing the elements
		System.out.println("Stack after insertion: " + s);

		// Removing elements from the Stack
		// using pop() operation
		s.pop();
		System.out.println("Stack after deletion: " + s);
		s.pop();
		System.out.println("Stack after deletion: "	+ s);
	}
}

Stack after insertion: [15, 19, 17]
Stack after deletion: [19, 17]
Stack after deletion: [17]

LinkedList Class

• Also implements Deque and can be used as a stack, queue, or double-ended queue. It is a doubly-linked list implementation.
• We use LinkedList when we want to leverage linked list operations like insertions and deletions are required at both ends.
• More memory overhead as we used linked list.