StackUSingLinkedList.java

public class StackUSingLinkedList {


// Driver code

// 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.print(temp.data);

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

}