import java.util.EmptyStackException;

import java.util.Iterator;

import java.util.LinkedList;

public class Stack <T> implements Iterable <T> {

private LinkedList <T> list = new java.util.LinkedList <T>();

// Create an empty stack

public Stack() { }

// Create a Stack with an initial element

public Stack(T firstElem) {

push(firstElem);

}

// Return the number of elements in the stack

public int size() {

return list.size();

}

// Check if the stack is empty

public boolean isEmpty() {

return size() == 0;

}

// Push an element on the stack

public void push(T elem) {

list.addLast(elem);

}

// Pop an element off the stack

// Throws an error is the stack empty

public T pop() {

if (isEmpty())

throw new EmptyStackException();

return list.removeLast();

}

// Peek the top of the stack without removing an element

// Throws an exception if the stack is empty

public T peek() {

if (isEmpty())

throw new EmptyStackException();

return list.peekLast();

}

// Allow users to iterate through the stack using an iterator

@Override public Iterator <T> iterator () {

return list.iterator();

}

}