question: protected void validateHole ( BaseLineStringBuilder shell , BaseLineStringBuilder hole ) { HashSet exterior = Sets . newHashSet ( shell . points ) ; HashSet interior = Sets . newHashSet ( hole . points ) ; exterior . retainAll ( interior ) ; if ( exterior . size ( ) >= 2 ) { throw new InvalidShapeException ( "Invalid polygon, interior cannot share more than one point with the exterior" ) ; } }
target:  Validates only 1 vertex is tangential (shared) between the interior and exterior of a polygon