Stack Link List

package DataS;

// Stack class using a linked list
public class StackLinkList {
    private Node top;  // Top of the stack
    
 // Node class to represent each element in the linked list
    class Node {
        int data;     // Data to be stored in the node
        Node next;    // Pointer to the next node in the list

        // Constructor to initialize the node with given data
        Node(int data) {
            this.data = data;
            this.next = null;
        }
    }

    // Constructor to initialize an empty stack
    public StackLinkList() {
        this.top = null;
    }

    // Method to check if the stack is empty
    public boolean isEmpty() {
        return top == null;
    }

    // Method to push a new element onto the stack
    public void push(int data) {
        Node newNode = new Node(data);  // Create a new node with the given data
        newNode.next = top;            // Set the next of new node as top
        top = newNode;                 // Move top to point to the new node
        System.out.println("Pushed " + data + " onto the stack.");
    }

    // Method to pop the top element from the stack
    public int pop() {
        if (isEmpty()) {
            System.out.println("Stack is empty. Cannot pop.");
            return -1;  // Return -1 or throw exception for empty stack scenario
        }
        int poppedData = top.data;    // Get the data from the top node
        top = top.next;               // Move top to point to the next node
        System.out.println("Popped " + poppedData + " from the stack.");
        return poppedData;
    }

    // Method to peek at the top element of the stack without removing it
    public int peek() {
        if (isEmpty()) {
            System.out.println("Stack is empty. Cannot peek.");
            return -1;  // Return -1 or throw exception for empty stack scenario
        }
        return top.data;  // Return data of the top node
    }

    // Method to print all elements currently in the stack
    public void printStack() {
        if (isEmpty()) {
            System.out.println("Stack is empty.");
            return;
        }
        System.out.println("Elements in the stack:");
        Node current = top;
        while (current != null) {
            System.out.println(current.data);
            current = current.next;
        }
    }

    // Main method to demonstrate the stack operations
    public static void main(String[] args) {
        StackLinkList stack = new StackLinkList();

        // Pushing elements onto the stack
        stack.push(20);
        stack.push(30);
        stack.push(40);
        stack.push(50);

        // Printing the stack
        stack.printStack();

        // Popping elements from the stack
        stack.pop();
        stack.pop();

        // Printing the stack after popping
        stack.printStack();

        // Peeking at the top element
        System.out.println("Top element of the stack: " + stack.peek());
    }
}