import java.util.EmptyStackException;

public class MyStack<E> implements StackInterface<E>
{
    MyStack()
    {
        data = (E[]) new Object[3];
        makeEmpty();
    }
    
    public void makeEmpty()
    {
        top = -1;
    }
    
    public boolean empty()
    {
        return (top == -1);
    }
    
    public E push (E item)
    {
        top++;
        if (top == data.length)
        {
            E [] newData = (E[]) new Object [data.length * 2];
            for (int i = 0; i < data.length; i++)
            {
                newData[i] = data[i];
            }
            data = newData;
        }
        data[top] = item;
        return item;
    }
    
    public E pop()throws EmptyStackException
    {
        if (empty())
        {
            throw new EmptyStackException();
        }
        else
        {
            top--;
            return(data[top+1]);  // notice the top + 1
        }
    }
    
    public E peek() throws EmptyStackException
    {
        if (empty())
        {
            throw new EmptyStackException();
        }
        else
        {
            return(data[top]);
        }
    }
    
    private E [] data;
    private int top;
}