public class MyStack {
	
	
	private Node first;
	private int elements;
	
	
	public MyStack(){
		//first = new Node(null); //don't add empty element!
		elements = 0;
	}
	
	
	/**
	 * Adds element to the list (head of list)
	 * @param element
	 */
	public void push(Object element){
		
		//the new element is the last in the list:
		Node old = first;
		first = new Node(element);
		first.setNext(old);
		elements++;
	} 
	
	/**
	 * Removes element from head of list
	 * @return
	 */
	public Object pop(){
		Object element = first.getItem();
		first = first.next;
		elements--;
		
		return element;
	}
	
	
	public void showElements(){
		
		Node current = first;
		while (current != null){
			System.out.println("Elements = " + current.getItem().toString());
			current = current.getNext();
		}
	}
	
	
	
	
	
	
	//Inner class with the data structure of the linked list	
	private class Node{
			
		//these are private
		Object item;
		Node next;
			
		//constructor
		public Node (Object value){
			next = null;
			item = value;
		}
			
		//standard getter and setter methods
		
		public Object getItem() {
			return item;
		}


		public void setItem(Object item) {
			this.item = item;
		}


		public Node getNext() {
			return next;
		}


		public void setNext(Node next) {
			this.next = next;
		}
	}
	
	
	

		
	//TESTS:
		
	public static void main(String[] args) {
		
		MyStack stack = new MyStack();
		stack.push("to");
		stack.push("be");
		stack.push("or");
		stack.showElements();
		System.out.println("pop....");
		stack.pop();
		stack.showElements();
		
		
	}



}