com.phoenixst.plexus.util.SingletonGraph.java Source code

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Here is the source code for com.phoenixst.plexus.util.SingletonGraph.java

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/*
 *  $Id: SingletonGraph.java,v 1.22 2006/06/07 20:25:53 rconner Exp $
 *
 *  Copyright (C) 1994-2006 by Phoenix Software Technologists,
 *  Inc. and others.  All rights reserved.
 *
 *  THIS PROGRAM AND DOCUMENTATION IS PROVIDED UNDER THE TERMS OF THE
 *  COMMON PUBLIC LICENSE ("AGREEMENT") WHICH ACCOMPANIES IT.  ANY
 *  USE, REPRODUCTION OR DISTRIBUTION OF THE PROGRAM CONSTITUTES
 *  RECIPIENT'S ACCEPTANCE OF THE AGREEMENT.
 *
 *  The license text can also be found at
 *    http://opensource.org/licenses/cpl.php
 */

package com.phoenixst.plexus.util;

import java.util.*;

import org.apache.commons.collections.Predicate;

import com.phoenixst.plexus.*;

/**
 *  An unmodifiable <code>Graph</code> which contains a single node
 *  and no edges.
 *
 *  @version    $Revision: 1.22 $
 *  @author     Ray A. Conner
 *
 *  @since      1.0
 */
public class SingletonGraph implements Graph, java.io.Serializable {

    private static final long serialVersionUID = 1L;

    /**
     *  The node.
     *
     *  @serial
     */
    private final Object singleNode;

    ////////////////////////////////////////
    // Constructor
    ////////////////////////////////////////

    /**
     *  Creates a new <code>SingletonGraph</code>.
     */
    public SingletonGraph(Object node) {
        super();
        singleNode = node;
    }

    ////////////////////////////////////////
    // Private check method
    ////////////////////////////////////////

    private void checkNode(Object node) {
        if (!GraphUtils.equals(singleNode, node)) {
            throw new NoSuchNodeException("Node is not in this graph: " + node);
        }
    }

    ////////////////////////////////////////
    // Graph methods
    ////////////////////////////////////////

    /**
     *  Throws an <code>UnsupportedOperationException</code>.
     */
    public boolean addNode(Object node) {
        throw new UnsupportedOperationException();
    }

    /**
     *  Throws an <code>UnsupportedOperationException</code>.
     */
    public boolean removeNode(Object node) {
        throw new UnsupportedOperationException();
    }

    public boolean containsNode(Object node) {
        return GraphUtils.equals(singleNode, node);
    }

    /**
     *  Throws an <code>UnsupportedOperationException</code>.
     */
    public Graph.Edge addEdge(Object object, Object tail, Object head, boolean isDirected) {
        throw new UnsupportedOperationException();
    }

    /**
     *  Throws an <code>UnsupportedOperationException</code>.
     */
    public boolean removeEdge(Graph.Edge edge) {
        throw new UnsupportedOperationException();
    }

    /**
     *  Returns <code>false</code>.
     */
    public boolean containsEdge(Graph.Edge edge) {
        return false;
    }

    public int degree(Object node) {
        checkNode(node);
        return 0;
    }

    public int degree(Object node, Predicate traverserPredicate) {
        checkNode(node);
        return 0;
    }

    public Collection nodes(Predicate nodePredicate) {
        return (nodePredicate == null || nodePredicate.evaluate(singleNode)) ? Collections.singleton(singleNode)
                : Collections.EMPTY_SET;
    }

    /**
     *  Returns an empty collection.
     */
    public Collection edges(Predicate edgePredicate) {
        return Collections.EMPTY_SET;
    }

    /**
     *  Returns an empty collection.
     */
    public Collection adjacentNodes(Object node, Predicate traverserPredicate) {
        checkNode(node);
        return Collections.EMPTY_SET;
    }

    /**
     *  Returns an empty collection.
     */
    public Collection incidentEdges(Object node, Predicate traverserPredicate) {
        checkNode(node);
        return Collections.EMPTY_SET;
    }

    public Object getNode(Predicate nodePredicate) {
        return (nodePredicate == null || nodePredicate.evaluate(singleNode)) ? singleNode : null;
    }

    /**
     *  Returns <code>null</code>.
     */
    public Graph.Edge getEdge(Predicate edgePredicate) {
        return null;
    }

    public Object getAdjacentNode(Object node, Predicate traverserPredicate) {
        checkNode(node);
        return null;
    }

    public Graph.Edge getIncidentEdge(Object node, Predicate traverserPredicate) {
        checkNode(node);
        return null;
    }

    public Traverser traverser(Object node, Predicate traverserPredicate) {
        checkNode(node);
        return GraphUtils.EMPTY_TRAVERSER;
    }

}