package examples;
import java.util.NoSuchElementException;

public interface Stack<T> {
	/**
	 * Test whether any elements are currently waiting on the stack.
	 * @return true if the stack is empty; false otherwise.
	 */
	boolean isEmpty();

	/**
	 * Returns the number of elements currently waiting on the stack.
	 * @return how many items are in this collection
	 */
	int size();

	/**
	 * Add an element to the top of the stack.
	 * @param e the element to add to this collection.
	 * @return true if the stack is not full and the element was succesfully
	 *    added; false otherwise.
	 */
	boolean push(T e);

	/**
	 * Removes the element from the top of the stack and returns it.
	 * @return null if the stack is empty; otherwise, the most recently
	 *     pushed element.
	 */
	T pop();

	/**
	 * Returns (but does not remove) the element at the top of the stack.
	 * @return null if the stack is empty; otherwise, the most recently
	 *     pushed element.
	 */
	T peek();
}