s.setParent(this);
    public void add(Stream s)    {        assert joiner == null;        // add the stream to the Split        if (splitter != null)            {                splitter.add(s);            }        // save the stream to add to the Join        if (childrenStreams == null)            {                childrenStreams = new LinkedList();            }        childrenStreams.add(s);    }