import java.util.Arrays;

public class Stack<E>
{
   private Object[] elements;
   private int currentSize;
   
   private static final int INITIAL_SIZE = 10;

   public Stack()
   {
      elements = new Object[INITIAL_SIZE]; 
      // elements = new E[INITIAL_SIZE] 
      // is an error--cannot make a generic array
   }

   public void push(E value)
   {
      if (currentSize >= elements.length) 
      {
         elements = Arrays.copyOf(elements, 2 * elements.length);
      }
      elements[currentSize] = value;
      currentSize++;
   }

   @SuppressWarnings("unchecked") // Suppresses "unchecked" warnings inside this method
   public E pop()
   {
      currentSize--;
      return (E) elements[currentSize]; // Cast causes "unchecked" warning
   }
   
   public int size() { return currentSize; }
}