PlanarGraph.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.planargraph;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import org.locationtech.jts.geom.Coordinate;
/**
* Represents a directed graph which is embeddable in a planar surface.
* <p>
* This class and the other classes in this package serve as a framework for
* building planar graphs for specific algorithms. This class must be
* subclassed to expose appropriate methods to construct the graph. This allows
* controlling the types of graph components ({@link DirectedEdge}s,
* {@link Edge}s and {@link Node}s) which can be added to the graph. An
* application which uses the graph framework will almost always provide
* subclasses for one or more graph components, which hold application-specific
* data and graph algorithms.
*
* @version 1.7
*/
public abstract class PlanarGraph
{
protected Set edges = new HashSet();
protected Set dirEdges = new HashSet();
protected NodeMap nodeMap = new NodeMap();
/**
* Constructs a empty graph.
*/
public PlanarGraph()
{
}
/**
* Returns the {@link Node} at the given location,
* or null if no {@link Node} was there.
*
* @param pt the location to query
* @return the node found
* or <code>null</code> if this graph contains no node at the location
*/
public Node findNode(Coordinate pt)
{
return (Node) nodeMap.find(pt);
}
/**
* Adds a node to the map, replacing any that is already at that location.
* Only subclasses can add Nodes, to ensure Nodes are of the right type.
*
* @param node the node to add
*/
protected void add(Node node)
{
nodeMap.add(node);
}
/**
* Adds the Edge and its DirectedEdges with this PlanarGraph.
* Assumes that the Edge has already been created with its associated DirectEdges.
* Only subclasses can add Edges, to ensure the edges added are of the right class.
*/
protected void add(Edge edge)
{
edges.add(edge);
add(edge.getDirEdge(0));
add(edge.getDirEdge(1));
}
/**
* Adds the Edge to this PlanarGraph; only subclasses can add DirectedEdges,
* to ensure the edges added are of the right class.
*/
protected void add(DirectedEdge dirEdge)
{
dirEdges.add(dirEdge);
}
/**
* Returns an Iterator over the Nodes in this PlanarGraph.
*/
public Iterator nodeIterator() { return nodeMap.iterator(); }
/**
* Returns the Nodes in this PlanarGraph.
*/
/**
* Tests whether this graph contains the given {@link Edge}
*
* @param e the edge to query
* @return <code>true</code> if the graph contains the edge
*/
public boolean contains(Edge e)
{
return edges.contains(e);
}
/**
* Tests whether this graph contains the given {@link DirectedEdge}
*
* @param de the directed edge to query
* @return <code>true</code> if the graph contains the directed edge
*/
public boolean contains(DirectedEdge de)
{
return dirEdges.contains(de);
}
public Collection getNodes() { return nodeMap.values(); }
/**
* Returns an Iterator over the DirectedEdges in this PlanarGraph, in the order in which they
* were added.
*
* @see #add(Edge)
* @see #add(DirectedEdge)
*/
public Iterator dirEdgeIterator() { return dirEdges.iterator(); }
/**
* Returns an Iterator over the Edges in this PlanarGraph, in the order in which they
* were added.
*
* @see #add(Edge)
*/
public Iterator edgeIterator() { return edges.iterator(); }
/**
* Returns the Edges that have been added to this PlanarGraph
* @see #add(Edge)
*/
public Collection getEdges() { return edges; }
/**
* Removes an {@link Edge} and its associated {@link DirectedEdge}s
* from their from-Nodes and from the graph.
* Note: This method does not remove the {@link Node}s associated
* with the {@link Edge}, even if the removal of the {@link Edge}
* reduces the degree of a {@link Node} to zero.
*/
public void remove(Edge edge)
{
remove(edge.getDirEdge(0));
remove(edge.getDirEdge(1));
edges.remove(edge);
edge.remove();
}
/**
* Removes a {@link DirectedEdge} from its from-{@link Node} and from this graph.
* This method does not remove the {@link Node}s associated with the DirectedEdge,
* even if the removal of the DirectedEdge reduces the degree of a Node to zero.
*/
public void remove(DirectedEdge de)
{
DirectedEdge sym = de.getSym();
if (sym != null) sym.setSym(null);
de.getFromNode().remove(de);
de.remove();
dirEdges.remove(de);
}
/**
* Removes a node from the graph, along with any associated DirectedEdges and
* Edges.
*/
public void remove(Node node)
{
// unhook all directed edges
List outEdges = node.getOutEdges().getEdges();
for (Iterator i = outEdges.iterator(); i.hasNext(); ) {
DirectedEdge de = (DirectedEdge) i.next();
DirectedEdge sym = de.getSym();
// remove the diredge that points to this node
if (sym != null) remove(sym);
// remove this diredge from the graph collection
dirEdges.remove(de);
Edge edge = de.getEdge();
if (edge != null) {
edges.remove(edge);
}
}
// remove the node from the graph
nodeMap.remove(node.getCoordinate());
node.remove();
}
/**
* Returns all Nodes with the given number of Edges around it.
*/
public List findNodesOfDegree(int degree)
{
List nodesFound = new ArrayList();
for (Iterator i = nodeIterator(); i.hasNext(); ) {
Node node = (Node) i.next();
if (node.getDegree() == degree)
nodesFound.add(node);
}
return nodesFound;
}
}