/* ITI 1121/1521. Introduction to Computer Science II
 * Assignment/Devoir 3
 *
 *
 */

public interface Collection<E> {

    /**
     * Returns an iterator over the elements in this collection.
     * 
     * @return an Iterator over the elements in this collection
     */

    public abstract Iterator<E> iterator();

    /**
     * Ensures that this collection contains the specified element.
     * Returns true if this collection changed as a result of the
     * call.  Returns false if this collection does not permit
     * duplicates and already contains the specified element.
     *
     * @param item element whose presence in this collection is to be ensured.
     * @return true if this collection changed as a result of the call.
     */

    public abstract boolean add( E item );

    /*
     * Removes a single instance of the specified element from this
     * collection, if it is present.  Returns true if this collection
     * contained the specified element (or equivalently, if this
     * collection changed as a result of the call).
     *
     * @param item element to be removed from this collection, if present.
     * @return true if this collection changed as a result of the call.
     */

    public abstract boolean remove( E item );

    /**
     * Returns true if this collection contains no elements.
     *
     * @return true if this collection contains no elements
     */

    public abstract boolean isEmpty();

}