code: @Override public final boolean cancel( boolean mayInterruptIfRunning ) {
      boolean did = false;
      synchronized(this) {        // Install the answer under lock
        if( !isCancelled() ) {
          did = true;             // Did cancel (was not cancelled already)
          _target.taskRemove(_tasknum);
          _target = null;         // Flag as canceled
  //        UDPTimeOutThread.PENDING.remove(this);
        }
        notifyAll();              // notify in any case
      }
      return did;
    }
docs: Attempt to cancel job