1 /*
2 * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.imageio.spi;
27
28 import java.io.Serializable;
29 import java.util.HashSet;
30 import java.util.Iterator;
31 import java.util.Set;
32
33 /**
34 * A node in a directed graph. In addition to an arbitrary
35 * {@code Object} containing user data associated with the node,
36 * each node maintains a {@code Set}s of nodes which are pointed
37 * to by the current node (available from {@code getOutNodes}).
38 * The in-degree of the node (that is, number of nodes that point to
39 * the current node) may be queried.
40 *
41 */
42 class DigraphNode<E> implements Cloneable, Serializable {
43 private static final long serialVersionUID = 5308261378582246841L;
44
45 /** The data associated with this node. */
46 protected E data;
47
48 /**
49 * A {@code Set} of neighboring nodes pointed to by this
50 * node.
51 */
52 protected Set<DigraphNode<E>> outNodes = new HashSet<>();
53
54 /** The in-degree of the node. */
55 protected int inDegree = 0;
56
57 /**
58 * A {@code Set} of neighboring nodes that point to this
59 * node.
60 */
61 private Set<DigraphNode<E>> inNodes = new HashSet<>();
62
63 public DigraphNode(E data) {
64 this.data = data;
65 }
66
67 /** Returns the {@code Object} referenced by this node. */
68 public E getData() {
69 return data;
70 }
71
72 /**
73 * Returns an {@code Iterator} containing the nodes pointed
74 * to by this node.
75 */
76 public Iterator<DigraphNode<E>> getOutNodes() {
77 return outNodes.iterator();
78 }
79
80 /**
81 * Adds a directed edge to the graph. The outNodes list of this
82 * node is updated and the in-degree of the other node is incremented.
83 *
84 * @param node a {@code DigraphNode}.
85 *
86 * @return {@code true} if the node was not previously the
87 * target of an edge.
88 */
89 public boolean addEdge(DigraphNode<E> node) {
90 if (outNodes.contains(node)) {
91 return false;
92 }
93
94 outNodes.add(node);
95 node.inNodes.add(this);
96 node.incrementInDegree();
97 return true;
98 }
99
100 /**
101 * Returns {@code true} if an edge exists between this node
102 * and the given node.
103 *
104 * @param node a {@code DigraphNode}.
105 *
106 * @return {@code true} if the node is the target of an edge.
107 */
108 public boolean hasEdge(DigraphNode<E> node) {
109 return outNodes.contains(node);
110 }
111
112 /**
113 * Removes a directed edge from the graph. The outNodes list of this
114 * node is updated and the in-degree of the other node is decremented.
115 *
116 * @return {@code true} if the node was previously the target
117 * of an edge.
118 */
119 public boolean removeEdge(DigraphNode<E> node) {
120 if (!outNodes.contains(node)) {
121 return false;
122 }
123
124 outNodes.remove(node);
125 node.inNodes.remove(this);
126 node.decrementInDegree();
127 return true;
128 }
129
130 /**
131 * Removes this node from the graph, updating neighboring nodes
132 * appropriately.
133 */
134 public void dispose() {
135 Object[] inNodesArray = inNodes.toArray();
136 for(int i=0; i<inNodesArray.length; i++) {
137 @SuppressWarnings("unchecked")
138 DigraphNode<E> node = (DigraphNode<E>)inNodesArray[i];
139 node.removeEdge(this);
140 }
141
142 Object[] outNodesArray = outNodes.toArray();
143 for(int i=0; i<outNodesArray.length; i++) {
144 @SuppressWarnings("unchecked")
145 DigraphNode<E> node = (DigraphNode<E>)outNodesArray[i];
146 removeEdge(node);
147 }
148 }
149
150 /** Returns the in-degree of this node. */
151 public int getInDegree() {
152 return inDegree;
153 }
154
155 /** Increments the in-degree of this node. */
156 private void incrementInDegree() {
157 ++inDegree;
158 }
159
160 /** Decrements the in-degree of this node. */
161 private void decrementInDegree() {
162 --inDegree;
163 }
164 }