/**
 * ITI 1521. Introduction ŕ l'informatique II
 * ITI 1121. Introduction to Computer Science II
 *
 * @author Marcel Turcotte, Université d'Ottawa/University of Ottawa
 */

public interface Stack<E> {

    /**
     * Tests if this Stack is empty.
     *
     * @return true if this Stack is empty; and false otherwise.
     */

    public abstract boolean isEmpty();

    /**
     * Returns a reference to the top element; does not change
     * the state of this Stack.
     *
     * @return The top element of this stack without removing it.
     */

    public abstract E peek();

    /**
     * Removes and returns the element at the top of this stack.
     *
     * @return The top element of this stack.
     */

    public abstract E pop();

    /**
     * Puts an element onto the top of this stack.
     *
     * @param element the element be put onto the top of this stack.
     */

    public abstract void push( E element);

    /**
     * Removes all the elements from this stack.  Immediately after a
     * call to the method clear() the method isEmpty() will return
     * true.
     */

    public abstract void clear();

}