code: public final void cancel () {
  		cancelRunningChildren(0);
  		Status previousStatus = status;
  		status = Status.CANCELLED;
  		if (tree.listeners != null && tree.listeners.size > 0) tree.notifyStatusUpdated(this, previousStatus);
  		end();
  	}
docs: Terminates this task and all its running children. This method MUST be called only if this task is running.