question: public synchronized void unregister ( String name ) { StreamScope < ? > streamScope = byNameMap . remove ( name ) ; if ( streamScope == null ) return ; List < String > names = byStreamScopeMap . get ( streamScope ) ; names . remove ( name ) ; if ( names . isEmpty ( ) ) byStreamScopeMap . remove ( streamScope ) ; }
target:  remove the specific name registration.  Other registration of the same StreamScope may still exist. no-op if name is not registered.