Interface Runnable question (Newbie)

From: Zalek Bloom (ZalekBloom_at_hotmail.com)
Date: 10/28/03 

Date: Tue, 28 Oct 2003 02:48:09 GMT

I am learning Threads. One of the options to create a Thread in to use
the Runnable interface. The Runnable interface looks:

public interface Runnable {
    public abstract void run();
}

My question:
Why do we need to implemement Runnable - why not just to define the
run() method without writing "implements Runnable"?

Zalek