StackUsingLL.java

import java.util.*;
public class StackUsingLL{
    public static class Stack{
            static class Node{
            int data;
            Node next;
            Node(int data){
                this.data=data;
                this.next=null;
            }
        }
        public static Node head=null;
        public static boolean isEmpty(){
            return head==null;
        }
        public static void push(int data){
            Node newNode=new Node(data);
            if (isEmpty()){
                head=newNode;
                return;
            }
            newNode.next=head;
            head=newNode;
        }
        public static int pop(){
            if (isEmpty()){
                return -1;
            }
            int top=head.data;
            head=head.next;
            return top;
        }
        public static int peek(){
            if (isEmpty()){
                return -1;
            }
            return head.data;
        }
    }
    public static void main(String[] args) {
        Stack.push(30);
        Stack.push(20);
        Stack.push(30);
        while(!Stack.isEmpty()){
            System.out.println("Top: " + Stack.peek());
            Stack.pop();
        }
    }
}