Implement Stack using Linked List Java

PROGRAM TO IMPLEMENT STACK USING SINGLY LINKED LIST

import static java.lang.System.exit;

 

// Create Stack Using Linked list

class StackUsingLinkedlist {

 

    // A linked list node

    private class Node {

 

        int data; // integer data

        Node link; // reference variable Node type

    }

    // create global top reference variable global

    Node top;

    // Constructor

    StackUsingLinkedlist()

    {

        this.top = null;

    }

 

    // Utility function to add an element x in the stack

    public void push(int x) // insert at the beginning

    {

        // create new node temp and allocate memory

        Node temp = new Node();

 

        // check if stack (heap) is full. Then inserting an

        //  element would lead to stack overflow

        if (temp == null) {

            System.out.print("\nHeap Overflow");

            return;

        }

 

        // initialize data into temp data field

        temp.data = x;

 

        // put top reference into temp link

        temp.link = top;

 

        // update top reference

        top = temp;

    }

 

    // Utility function to check if the stack is empty or not

    public boolean isEmpty()

    {

        return top == null;

    }

 

    // Utility function to return top element in a stack

    public int peek()

    {

        // check for empty stack

        if (!isEmpty()) {

            return top.data;

        }

        else {

            System.out.println("Stack is empty");

            return -1;

        }

    }

 

    // Utility function to pop top element from the stack

    public void pop() // remove at the beginning

    {

        // check for stack underflow

        if (top == null) {

            System.out.print("\nStack Underflow");

            return;

        }

 

        // update the top pointer to point to the next node

        top = (top).link;

    }

 

    public void display()

    {

        // check for stack underflow

        if (top == null) {

            System.out.printf("\nStack Underflow");

            exit(1);

        }

        else {

            Node temp = top;

            while (temp != null) {

 

                // print node data

                System.out.printf("%d->", temp.data);

 

                // assign temp link to temp

                temp = temp.link;

            }

        }

    }

}

// main class

public class GFG {

    public static void main(String[] args)

    {

        // create Object of Implementing class

        StackUsingLinkedlist obj = new StackUsingLinkedlist();

        // insert Stack value

        obj.push(11);

        obj.push(22);

        obj.push(33);

        obj.push(44);

 

        // print Stack elements

        obj.display();

 

        // print Top element of Stack

        System.out.printf("\nTop element is %d\n", obj.peek());

 

        // Delete top element of Stack

        obj.pop();

        obj.pop();

 

        // print Stack elements

        obj.display();

 

        // print Top element of Stack

        System.out.printf("\nTop element is %d\n", obj.peek());

    }

}

OUTPUT:

44->33->22->11->
Top element is 44
22->11->
Top element is 22

CREDITS: https://www.geeksforgeeks.org/implement-a-stack-using-singly-linked-list/