public Set < String > getNamesPerSurname ( final String surname ) { if ( surname == null ) { return Collections . emptySet ( ) ; } if ( ! surnameIndex . containsKey ( surname ) ) { return Collections . emptySet ( ) ; } return Collections . unmodifiableSet ( surnameIndex . get ( surname ) . keySet ( ) ) ; }
Get the set of full names that occur for a given surname .