code: public boolean isAdjacent(Geometry geometry, GeometryIndex one, GeometryIndex two) {
  		List<GeometryIndex> neighbors = null;
  		try {
  			if (isVertex(two)) {
  				neighbors = getAdjacentVertices(geometry, one);
  			} else if (isEdge(two)) {
  				neighbors = getAdjacentEdges(geometry, one);
  			}
  		} catch (GeometryIndexNotFoundException e) {
  			return false;
  		}
  
  		if (neighbors != null) {
  			for (GeometryIndex neighbor : neighbors) {
  				if (neighbor.equals(two)) {
  					return true;
  				}
  			}
  		}
  
  		return false;
  	}
docs: Given a certain geometry and index (one), check if the the other index (two) is a neighbor.
  
  @param geometry
  The geometry wherein to search if indices one and two are neighbors.
  @param one
  One of the indices. Must point to either a vertex or and edge.
  @param two
  Another one of the indices. Must point to either a vertex or and edge.
  @return true or false.