code: static boolean _isRingInRing2D(MultiPath polygon, int iRing1, int iRing2,
  			double tolerance, QuadTree quadTree) {
  		MultiPathImpl polygonImpl = (MultiPathImpl) polygon._getImpl();
  		SegmentIteratorImpl segIter = polygonImpl.querySegmentIterator();
  		segIter.resetToPath(iRing1);
  		if (!segIter.nextPath() || !segIter.hasNextSegment())
  			throw new GeometryException("corrupted geometry");
  
  		int res = 2;
  
  		while (res == 2 && segIter.hasNextSegment()) {
  			Segment segment = segIter.nextSegment();
  			Point2D point = segment.getCoord2D(0.5);
  			res = PointInPolygonHelper.isPointInRing(polygonImpl, iRing2,
  					point, tolerance, quadTree);
  		}
  
  		if (res == 2)
  			throw GeometryException.GeometryInternalError();
  		if (res == 1)
  			return true;
  
  		return false;
  	}
docs: we assume that all of Ring1 is inside Ring2.