001 /*
002 * Copyright 2000 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package javax.imageio.spi;
027
028 import java.io.Serializable;
029 import java.util.HashSet;
030 import java.util.Iterator;
031 import java.util.Set;
032
033 /**
034 * A node in a directed graph. In addition to an arbitrary
035 * <code>Object</code> containing user data associated with the node,
036 * each node maintains a <code>Set</code>s of nodes which are pointed
037 * to by the current node (available from <code>getOutNodes</code>).
038 * The in-degree of the node (that is, number of nodes that point to
039 * the current node) may be queried.
040 *
041 * @version 0.5
042 */
043 class DigraphNode implements Cloneable, Serializable {
044
045 /** The data associated with this node. */
046 protected Object data;
047
048 /**
049 * A <code>Set</code> of neighboring nodes pointed to by this
050 * node.
051 */
052 protected Set outNodes = new HashSet();
053
054 /** The in-degree of the node. */
055 protected int inDegree = 0;
056
057 /**
058 * A <code>Set</code> of neighboring nodes that point to this
059 * node.
060 */
061 private Set inNodes = new HashSet();
062
063 public DigraphNode(Object data) {
064 this .data = data;
065 }
066
067 /** Returns the <code>Object</code> referenced by this node. */
068 public Object getData() {
069 return data;
070 }
071
072 /**
073 * Returns an <code>Iterator</code> containing the nodes pointed
074 * to by this node.
075 */
076 public Iterator getOutNodes() {
077 return outNodes.iterator();
078 }
079
080 /**
081 * Adds a directed edge to the graph. The outNodes list of this
082 * node is updated and the in-degree of the other node is incremented.
083 *
084 * @param node a <code>DigraphNode</code>.
085 *
086 * @return <code>true</code> if the node was not previously the
087 * target of an edge.
088 */
089 public boolean addEdge(DigraphNode node) {
090 if (outNodes.contains(node)) {
091 return false;
092 }
093
094 outNodes.add(node);
095 node.inNodes.add(this );
096 node.incrementInDegree();
097 return true;
098 }
099
100 /**
101 * Returns <code>true</code> if an edge exists between this node
102 * and the given node.
103 *
104 * @param node a <code>DigraphNode</code>.
105 *
106 * @return <code>true</code> if the node is the target of an edge.
107 */
108 public boolean hasEdge(DigraphNode 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</code> if the node was previously the target
117 * of an edge.
118 */
119 public boolean removeEdge(DigraphNode 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 DigraphNode node = (DigraphNode) inNodesArray[i];
138 node.removeEdge(this );
139 }
140
141 Object[] outNodesArray = outNodes.toArray();
142 for (int i = 0; i < outNodesArray.length; i++) {
143 DigraphNode node = (DigraphNode) outNodesArray[i];
144 removeEdge(node);
145 }
146 }
147
148 /** Returns the in-degree of this node. */
149 public int getInDegree() {
150 return inDegree;
151 }
152
153 /** Increments the in-degree of this node. */
154 private void incrementInDegree() {
155 ++inDegree;
156 }
157
158 /** Decrements the in-degree of this node. */
159 private void decrementInDegree() {
160 --inDegree;
161 }
162 }
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