public class LinkedListStack<T> implements Stack {

	private class Node {
		Node next;
		Object element;
	}

	private Node head = new Node();
	private int size;
	@Override
	public boolean isEmpty() {
		return head.next == null;
	}

	@Override
	public boolean isFull() {
		return false;
	}

	@Override
	public int size() {
		return size;
	}

	@Override
	public Object top() throws StackEmptyException {
		if (isEmpty()) {
			throw new StackEmptyException();
		}
		
		return head.next.element;
	}

	@Override
	public void push(Object element) throws StackFullException {
		Node node = new Node();
		node.next = head.next;
		head.next = node;
		node.element = element;
		size++;
	}

	@Override
	public Object pop() throws StackEmptyException {
		if (isEmpty()) {
			throw new StackEmptyException();
		}
		
		Object element = head.next.element;
		head.next = head.next.next;
		size--;
		return element;
	}

	@Override
	public void empty() {
		head.next = null;
	}
}