Is this code "proper" use of extend?

CJ <>
Thu, 29 Nov 2007 09:24:52 -0800 (PST)
Thanks in advance for your responses.

I am relatively new to OOP and though I have muscled my way through
Java, I am still trying to correctly understand the concepts of OO and
how then are modeled into Java.

I am a thirty year procedural language developer, c and assembler, to
this (recent) technology called Object Oriented whatever is somewhat
alien to my experiences. I think I grasp the basic concepts of OO,
that being describing concrete "objects" as a series of refinements to
abstract "conceptual objects." (Please don't flame me if that
statement is incorrect, I am seeking to increase my understanding.)

The following Java 1.5 code I believe demonstrates the statement
above. I needed Vector container that would notify() all active
Objects it contains. My thinking was to simply extend Vector adding
the functionality I wanted.

However, a co-worker is rather irate at me for "doing such a silly
thing," preferring instead to Instantiate a Vector object with
SignaledVector, and implement the entire Vector contract method by
method. That just sounds contrary to principles OO.

Your thoughts?

import java.util.Collection;
import java.util.Vector;

public class SignaledVector<E> extends Vector<E>
    public SignaledVector()
    } // public SignaledVector()

    public SignaledVector(int initialCapacity)
    } // public SignaledVector(int initialCapacity)

    public SignaledVector(int initialCapacity,int capacityIncrement)
    } // public SignaledVector(int initialCapacity,int

    public SignaledVector(Collection<? extends E> c)
    } // public SignaledVector(Collection<? extends E> c)

    //public synchronized boolean add(E e) { return(super.add(e)); }

     * Sends a signal to the object that has posted a {@code
     * @param index the index in the element to signal
     * @return the component at the specified index
     * @throws ArrayIndexOutOfBoundsException
    public E signal(int index)
        throws ArrayIndexOutOfBoundsException
        E element = get(index);
        synchronized(element) { element.notify(); }
    } // public final void signal<E>(int index)

     * Sends a signal to the object that has posted a {@code
     * This method sends a {@code synchronized} signal to all elements
     * contained in the {@code SignaledVector}
     * @throws ArrayIndexOutOfBoundsException
    public synchronized void signalAll()
        throws ArrayIndexOutOfBoundsException,
        java.util.Enumeration<E> threads = elements();

            E element = threads.nextElement();
            if (null == element) continue;
            synchronized(element) { element.notify(); }
        } // while(threads.hasMoreElements())
    } // public final void signalAll()
} // public class SignaledVector<E> extends Vector<E>


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