public Subcollection createSubCollection(final String id,final String name){
  Subcollection subCol=null;
  if (!collectionMap.containsKey(id)) {
    subCol=new Subcollection(id,name,getConf());
    collectionMap.put(id,subCol);
  }
  return subCol;
}

public Subcollection createSubCollection ( final String id , final String name ) { Subcollection subCol = null ; if ( ! collectionMap . containsKey ( id ) ) { subCol = new Subcollection ( id , name , getConf ( ) ) ; collectionMap . put ( id , subCol ) ; } return subCol ; }
create a new subcollection .
