com.vividsolutions.jts.geom.util.GeometryCombiner Maven / Gradle / Ivy
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/*
* 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);
}
}
}