public void cleanUp(){
  topSnapshot.set(null);
  singleMsgs.clear();
  fullMsgs.clear();
  crd=null;
  partReleaseFut=null;
}

public void cleanUp ( ) { topSnapshot . set ( null ) ; singleMsgs . clear ( ) ; fullMsgs . clear ( ) ; crd = null ; partReleaseFut = null ; }
cleans up resources to avoid excessive memory usage .
