public List < String > makeKey ( final Map < MetaKey , String > metaData , final boolean requireAll ) { final List < String > result = new ArrayList <> ( this . fields . size ( ) ) ; for ( final MetaKey field : this . fields ) { final String value = metaData . get ( field ) ; if ( requireAll && value == null ) { return null ; } result . add ( value ) ; } return result ; }
Make a key from the aggregator fields