/* * The JTS Topology Suite is a collection of Java classes that * implement the fundamental operations required to validate a given * geo-spatial data set to a known topological specification. * * Copyright (C) 2001 Vivid Solutions * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * * For more information, contact: * * Vivid Solutions * Suite #1A * 2328 Government Street * Victoria BC V8T 5G5 * Canada * * (250)385-6040 * www.vividsolutions.com */ package com.vividsolutions.jts.geom.util; import java.util.*; import com.vividsolutions.jts.geom.*; /** * Combines {@link Geometry}s * to produce a {@link GeometryCollection} of the most appropriate type. * Input geometries which are already collections * will have their elements extracted first. * No validation of the result geometry is performed. * (The only case where invalidity is possible is where {@link Polygonal} geometries * are combined and result in a self-intersection). * * @author mbdavis * @see GeometryFactory#buildGeometry */ public class GeometryCombiner { /** * Combines a collection of geometries. * * @param geoms the geometries to combine * @return the combined geometry */ public static Geometry combine(Collection geoms) { GeometryCombiner combiner = new GeometryCombiner(geoms); return combiner.combine(); } /** * Combines two geometries. * * @param g0 a geometry to combine * @param g1 a geometry to combine * @return the combined geometry */ public static Geometry combine(Geometry g0, Geometry g1) { GeometryCombiner combiner = new GeometryCombiner(createList(g0, g1)); return combiner.combine(); } /** * Combines three geometries. * * @param g0 a geometry to combine * @param g1 a geometry to combine * @param g2 a geometry to combine * @return the combined geometry */ public static Geometry combine(Geometry g0, Geometry g1, Geometry g2) { GeometryCombiner combiner = new GeometryCombiner(createList(g0, g1, g2)); return combiner.combine(); } /** * Creates a list from two items * * @param obj0 * @param obj1 * @return a List containing the two items */ private static List createList(Object obj0, Object obj1) { List list = new ArrayList(); list.add(obj0); list.add(obj1); return list; } /** * Creates a list from two items * * @param obj0 * @param obj1 * @return a List containing the two items */ private static List createList(Object obj0, Object obj1, Object obj2) { List list = new ArrayList(); list.add(obj0); list.add(obj1); list.add(obj2); return list; } private GeometryFactory geomFactory; private boolean skipEmpty = false; private Collection inputGeoms; /** * Creates a new combiner for a collection of geometries * * @param geoms the geometries to combine */ public GeometryCombiner(Collection geoms) { geomFactory = extractFactory(geoms); this.inputGeoms = geoms; } /** * Extracts the GeometryFactory used by the geometries in a collection * * @param geoms * @return a GeometryFactory */ public static GeometryFactory extractFactory(Collection geoms) { if (geoms.isEmpty()) return null; return ((Geometry) geoms.iterator().next()).getFactory(); } /** * Computes the combination of the input geometries * to produce the most appropriate {@link Geometry} or {@link GeometryCollection} * * @return a Geometry which is the combination of the inputs */ public Geometry combine() { List elems = new ArrayList(); for (Iterator i = inputGeoms.iterator(); i.hasNext(); ) { Geometry g = (Geometry) i.next(); extractElements(g, elems); } if (elems.size() == 0) { if (geomFactory != null) { // return an empty GC return geomFactory.createGeometryCollection(null); } return null; } // return the "simplest possible" geometry return geomFactory.buildGeometry(elems); } private void extractElements(Geometry geom, List elems) { if (geom == null) return; for (int i = 0; i < geom.getNumGeometries(); i++) { Geometry elemGeom = geom.getGeometryN(i); if (skipEmpty && elemGeom.isEmpty()) continue; elems.add(elemGeom); } } }