DigraphNode.java

/*
   Copyright (C) 2005-2012, by the President and Fellows of Harvard College.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

         http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

   Dataverse Network - A web application to share, preserve and analyze research data.
   Developed at the Institute for Quantitative Social Science, Harvard University.
   Version 3.0.
*/

package edu.harvard.iq.dataverse.ingest.plugin.spi;

// This file was Taken out from openjdk-6-src-b16-24_apr_2009.tar.gz
// http://download.java.net/openjdk/jdk6/promoted/b16/openjdk-6-src-b16-24_apr_2009.tar.gz
// downloaded: 2009-05-07


/*
 * Copyright 2000 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

//package javax.imageio.spi;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * A node in a directed graph.  In addition to an arbitrary
 * <code>Object</code> containing user data associated with the node,
 * each node maintains a <code>Set</code>s of nodes which are pointed
 * to by the current node (available from <code>getOutNodes</code>).
 * The in-degree of the node (that is, number of nodes that point to
 * the current node) may be queried.
 *
 */
class DigraphNode implements Cloneable, Serializable {

    /** The data associated with this node. */
    protected Object data;

    /**
     * A <code>Set</code> of neighboring nodes pointed to by this
     * node.
     */
    protected Set outNodes = new HashSet();

    /** The in-degree of the node. */
    protected int inDegree = 0;

    /**
     * A <code>Set</code> of neighboring nodes that point to this
     * node.
     */
    private Set inNodes = new HashSet();

    public DigraphNode(Object data) {
        this.data = data;
    }

    /** Returns the <code>Object</code> referenced by this node. */
    public Object getData() {
        return data;
    }

    /**
     * Returns an <code>Iterator</code> containing the nodes pointed
     * to by this node.
     */
    public Iterator getOutNodes() {
        return outNodes.iterator();
    }

    /**
     * Adds a directed edge to the graph.  The outNodes list of this
     * node is updated and the in-degree of the other node is incremented.
     *
     * @param node a <code>DigraphNode</code>.
     *
     * @return <code>true</code> if the node was not previously the
     * target of an edge.
     */
    public boolean addEdge(DigraphNode node) {
        if (outNodes.contains(node)) {
            return false;
        }

        outNodes.add(node);
        node.inNodes.add(this);
        node.incrementInDegree();
        return true;
    }

    /**
     * Returns <code>true</code> if an edge exists between this node
     * and the given node.
     *
     * @param node a <code>DigraphNode</code>.
     *
     * @return <code>true</code> if the node is the target of an edge.
     */
    public boolean hasEdge(DigraphNode node) {
        return outNodes.contains(node);
    }

    /**
     * Removes a directed edge from the graph.  The outNodes list of this
     * node is updated and the in-degree of the other node is decremented.
     *
     * @return <code>true</code> if the node was previously the target
     * of an edge.
     */
    public boolean removeEdge(DigraphNode node) {
        if (!outNodes.contains(node)) {
            return false;
        }

        outNodes.remove(node);
        node.inNodes.remove(this);
        node.decrementInDegree();
        return true;
    }

    /**
     * Removes this node from the graph, updating neighboring nodes
     * appropriately.
     */
    public void dispose() {
        Object[] inNodesArray = inNodes.toArray();
        for(int i=0; i<inNodesArray.length; i++) {
            DigraphNode node = (DigraphNode) inNodesArray[i];
            node.removeEdge(this);
        }

        Object[] outNodesArray = outNodes.toArray();
        for(int i=0; i<outNodesArray.length; i++) {
            DigraphNode node = (DigraphNode) outNodesArray[i];
            removeEdge(node);
        }
    }

    /** Returns the in-degree of this node. */
    public int getInDegree() {
        return inDegree;
    }

    /** Increments the in-degree of this node. */
    private void incrementInDegree() {
        ++inDegree;
    }

    /** Decrements the in-degree of this node. */
    private void decrementInDegree() {
        --inDegree;
    }
}