question: public SpatialStrategy ( SpatialContext ctx , String fieldName ) { if ( ctx == null ) throw new IllegalArgumentException ( "ctx is required" ) ; this . ctx = ctx ; if ( fieldName == null || fieldName . length ( ) == 0 ) throw new IllegalArgumentException ( "fieldName is required" ) ; this . fieldName = fieldName ; }
target:  Constructs the spatial strategy with its mandatory arguments.