Class Subgraph

1	/*
2	* Copyright (c) 2016 Vivid Solutions.
3	*
4	* All rights reserved. This program and the accompanying materials
5	* are made available under the terms of the Eclipse Public License 2.0
6	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8	* and the Eclipse Distribution License is available at
9	*
10	* http://www.eclipse.org/org/documents/edl-v10.php.
11	*/
12
13	package org.locationtech.jts.planargraph;
14
15	import java.util.ArrayList;
16	import java.util.HashSet;
17	import java.util.Iterator;
18	import java.util.List;
19	import java.util.Set;
20
21	/**
22	* A subgraph of a {@link PlanarGraph}.
23	* A subgraph may contain any subset of {@link Edge}s
24	* from the parent graph.
25	* It will also automatically contain all {@link DirectedEdge}s
26	* and {@link Node}s associated with those edges.
27	* No new objects are created when edges are added -
28	* all associated components must already exist in the parent graph.
29	*/
30	public class Subgraph
31	{
32	protected PlanarGraph parentGraph;
33	protected Set edges = new HashSet();
34	protected List dirEdges = new ArrayList();
35	protected NodeMap nodeMap = new NodeMap();
36
37	/**
38	* Creates a new subgraph of the given {@link PlanarGraph}
39	*
40	* @param parentGraph the parent graph
41	*/
42	public Subgraph(PlanarGraph parentGraph) {
43	this.parentGraph = parentGraph;
44	}
45
46	/**
47	* Gets the {@link PlanarGraph} which this subgraph
48	* is part of.
49	*
50	* @return the parent PlanarGraph
51	*/
52	public PlanarGraph getParent()
53	{
54	return parentGraph;
55	}
56	/**
57	* Adds an {@link Edge} to the subgraph.
58	* The associated {@link DirectedEdge}s and {@link Node}s
59	* are also added.
60	*
61	* @param e the edge to add
62	*/
63	public void add(Edge e)
64	{
65	if (edges.contains(e)) return;
66
67	edges.add(e);
68	dirEdges.add(e.getDirEdge(0));
69	dirEdges.add(e.getDirEdge(1));
70	nodeMap.add(e.getDirEdge(0).getFromNode());
71	nodeMap.add(e.getDirEdge(1).getFromNode());
72	}
73
74	/**
75	* Returns an {@link Iterator} over the {@link DirectedEdge}s in this graph,
76	* in the order in which they were added.
77	*
78	* @return an iterator over the directed edges
79	*
80	* @see #add(Edge)
81	*/
82	public Iterator dirEdgeIterator() { return dirEdges.iterator(); }
83
84	/**
85	* Returns an {@link Iterator} over the {@link Edge}s in this graph,
86	* in the order in which they were added.
87	*
88	* @return an iterator over the edges
89	*
90	* @see #add(Edge)
91	*/
92	public Iterator edgeIterator() { return edges.iterator(); }
93
94	/**
95	* Returns an {@link Iterator} over the {@link Node}s in this graph.
96	* @return an iterator over the nodes
97	*/
98	public Iterator nodeIterator() { return nodeMap.iterator(); }
99
100	/**
101	* Tests whether an {@link Edge} is contained in this subgraph
102	* @param e the edge to test
103	* @return <code>true</code> if the edge is contained in this subgraph
104	*/
105	public boolean contains(Edge e) { return edges.contains(e); }
106
107	}
108