stack_linked.java

import static java.lang.System.exit;


class stackusinglinkedlist {
	public static void main(String[] args)
	{
		
		StackUsingLinkedlist obj
			= new StackUsingLinkedlist();
		obj.push(11);
		obj.push(22);
		obj.push(33);
		obj.push(44);

		
		obj.display();

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

		
		obj.pop();
		obj.pop();

		
		obj.display();

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


class StackUsingLinkedlist {

	
	private class Node {

		int data; 
		Node link;
	}

	Node top;
	
	StackUsingLinkedlist() { this.top = null; }


	public void push(int x) 
	{
		
		Node temp = new Node();

		
		if (temp == null) {
			System.out.print("\nHeap Overflow");
			return;
		}

		
		temp.data = x;


		temp.link = top;

	
		top = temp;
	}

	
	public boolean isEmpty() { return top == null; }

	
	public int peek()
	{
		
		if (!isEmpty()) {
			return top.data;
		}
		else {
			System.out.println("Stack is empty");
			return -1;
		}
	}


	public void pop() 
	{
		
		if (top == null) {
			System.out.print("\nStack Underflow");
			return;
		}

		
		top = (top).link;
	}

	public void display()
	{
		
		if (top == null) {
			System.out.printf("\nStack Underflow");
			exit(1);
		}
		else {
			Node temp = top;
			while (temp != null) {

				
				System.out.print(temp.data);

				
				temp = temp.link;
				if(temp != null)
					System.out.print(" -> ");
			}
		}
	}
}