GeometryCombiner.java
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.geom.util;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryCollection;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.Polygonal;
/**
* 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();
}
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);
}
}
}