Class DirectedEdgeStar

1
2	/*
3	* Copyright (c) 2016 Vivid Solutions.
4	*
5	* All rights reserved. This program and the accompanying materials
6	* are made available under the terms of the Eclipse Public License 2.0
7	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
8	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
9	* and the Eclipse Distribution License is available at
10	*
11	* http://www.eclipse.org/org/documents/edl-v10.php.
12	*/
13
14
15	package org.locationtech.jts.planargraph;
16
17	import java.util.ArrayList;
18	import java.util.Collections;
19	import java.util.Iterator;
20	import java.util.List;
21
22	import org.locationtech.jts.geom.Coordinate;
23
24	/**
25	* A sorted collection of {@link DirectedEdge}s which leave a {@link Node}
26	* in a {@link PlanarGraph}.
27	*
28	* @version 1.7
29	*/
30	public class DirectedEdgeStar
31	{
32
33	/**
34	* The underlying list of outgoing DirectedEdges
35	*/
36	protected List outEdges = new ArrayList();
37	private boolean sorted = false;
38
39	/**
40	* Constructs a DirectedEdgeStar with no edges.
41	*/
42	public DirectedEdgeStar() {
43	}
44	/**
45	* Adds a new member to this DirectedEdgeStar.
46	*/
47	public void add(DirectedEdge de)
48	{
49	outEdges.add(de);
50	sorted = false;
51	}
52	/**
53	* Drops a member of this DirectedEdgeStar.
54	*/
55	public void remove(DirectedEdge de)
56	{
57	outEdges.remove(de);
58	}
59	/**
60	* Returns an Iterator over the DirectedEdges, in ascending order by angle with the positive x-axis.
61	*/
62	public Iterator iterator()
63	{
64	sortEdges();
65	return outEdges.iterator();
66	}
67
68	/**
69	* Returns the number of edges around the Node associated with this DirectedEdgeStar.
70	*/
71	public int getDegree() { return outEdges.size(); }
72
73	/**
74	* Returns the coordinate for the node at which this star is based
75	*/
76	public Coordinate getCoordinate()
77	{
78	Iterator it = iterator();
79	if (! it.hasNext()) return null;
80	DirectedEdge e = (DirectedEdge) it.next();
81	return e.getCoordinate();
82	}
83
84	/**
85	* Returns the DirectedEdges, in ascending order by angle with the positive x-axis.
86	*/
87	public List getEdges()
88	{
89	sortEdges();
90	return outEdges;
91	}
92
93	private void sortEdges()
94	{
95	if (! sorted) {
96	Collections.sort(outEdges);
97	sorted = true;
98	}
99	}
100	/**
101	* Returns the zero-based index of the given Edge, after sorting in ascending order
102	* by angle with the positive x-axis.
103	*/
104	public int getIndex(Edge edge)
105	{
106	sortEdges();
107	for (int i = 0; i < outEdges.size(); i++) {
108	DirectedEdge de = (DirectedEdge) outEdges.get(i);
109	if (de.getEdge() == edge)
110	return i;
111	}
112	return -1;
113	}
114	/**
115	* Returns the zero-based index of the given DirectedEdge, after sorting in ascending order
116	* by angle with the positive x-axis.
117	*/
118	public int getIndex(DirectedEdge dirEdge)
119	{
120	sortEdges();
121	for (int i = 0; i < outEdges.size(); i++) {
122	DirectedEdge de = (DirectedEdge) outEdges.get(i);
123	if (de == dirEdge)
124	return i;
125	}
126	return -1;
127	}
128	/**
129	* Returns value of i modulo the number of edges in this DirectedEdgeStar
130	* (i.e. the remainder when i is divided by the number of edges)
131	*
132	* @param i an integer (positive, negative or zero)
133	*/
134	public int getIndex(int i)
135	{
136	int modi = i % outEdges.size();
137	//I don't think modi can be 0 (assuming i is positive) [Jon Aquino 10/28/2003]
138	if (modi < 0) modi += outEdges.size();
139	return modi;
140	}
141
142	/**
143	* Returns the {@link DirectedEdge} on the left-hand (CCW)
144	* side of the given {@link DirectedEdge}
145	* (which must be a member of this DirectedEdgeStar).
146	*/
147	public DirectedEdge getNextEdge(DirectedEdge dirEdge)
148	{
149	int i = getIndex(dirEdge);
150	return (DirectedEdge) outEdges.get(getIndex(i + 1));
151	}
152
153	/**
154	* Returns the {@link DirectedEdge} on the right-hand (CW)
155	* side of the given {@link DirectedEdge}
156	* (which must be a member of this DirectedEdgeStar).
157	*/
158	public DirectedEdge getNextCWEdge(DirectedEdge dirEdge)
159	{
160	int i = getIndex(dirEdge);
161	return (DirectedEdge) outEdges.get(getIndex(i - 1));
162	}
163	}
164