Q: When is a thread active?

A: At first glance, this seems to be a simple question. Using the isAlive()
   method, a thread is considered alive during the period between the call
   to the start() method and a short time period after the stop() method is
   called. We might consider a thread active if it is alive.

   However, if the definition of an active thread is a thread whose thread
   reference appears in the active count returned by the activeCount() method,
   we would have a differenct definition of active. A thread reference first
   appears in the thread array returned by the enumerate() method, and is 
   counted by the activeCount() method, when the thread object is first
   constructed and not when the thread is started. [using the start() method.]

   The thread is removed from the thread array either when the thread is
   stopped or when the run() method has completed. This means that if a thread
   object is constructed but is not started, the thread object will not be
   removed from the enumeration list, even if the original reference to the
   object is lost.