001/* Computation of self-loops in a graph.
002
003 Copyright (c) 2003-2014 The University of Maryland. All rights reserved.
004 Permission is hereby granted, without written agreement and without
005 license or royalty fees, to use, copy, modify, and distribute this
006 software and its documentation for any purpose, provided that the above
007 copyright notice and the following two paragraphs appear in all copies
008 of this software.
009
010 IN NO EVENT SHALL THE UNIVERSITY OF MARYLAND BE LIABLE TO ANY PARTY
011 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
012 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
013 THE UNIVERSITY OF MARYLAND HAS BEEN ADVISED OF THE POSSIBILITY OF
014 SUCH DAMAGE.
015
016 THE UNIVERSITY OF MARYLAND SPECIFICALLY DISCLAIMS ANY WARRANTIES,
017 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
018 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
019 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
020 MARYLAND HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
021 ENHANCEMENTS, OR MODIFICATIONS.
022
023
024 */
025package ptolemy.graph.analysis.strategy;
026
027import java.util.ArrayList;
028import java.util.Collections;
029import java.util.Iterator;
030import java.util.List;
031
032import ptolemy.graph.Edge;
033import ptolemy.graph.Graph;
034import ptolemy.graph.analysis.analyzer.SelfLoopAnalyzer;
035
036///////////////////////////////////////////////////////////////////
037//// SelfLoopAnalyzer
038
039/**
040 Computation of self-loops in a graph.
041 The returned collection cannot be modified.
042 <p>
043 This analysis requires <em>O</em>(<em>E</em>) time, where <em>E</em> is the
044 number of edges in the graph.
045 <p>
046 @see ptolemy.graph.analysis.SelfLoopAnalysis
047 @since Ptolemy II 4.0
048 @Pt.ProposedRating Red (ssb)
049 @Pt.AcceptedRating Red (ssb)
050 @author Shuvra S. Bhattacharyya, Shahrooz Shahparnia
051 @version $Id$
052 */
053public class SelfLoopStrategy extends CachedStrategy
054        implements SelfLoopAnalyzer {
055    /** Construct an instance of this strategy for a given graph.
056     *
057     *  @param graph The given graph.
058     */
059    public SelfLoopStrategy(Graph graph) {
060        super(graph);
061    }
062
063    ///////////////////////////////////////////////////////////////////
064    ////                         public methods                    ////
065
066    /** Compute the self-loop edges in the graph in the form of
067     *  a collection. Each element of the collection is an {@link Edge}.
068     *  @return The self-loop edges.
069     */
070    @Override
071    public List edges() {
072        return (List) _result();
073    }
074
075    /** Return a description of the analyzer.
076     *
077     *  @return Return a description of the analyzer..
078     */
079    @Override
080    public String toString() {
081        return "Ordinary Self-loop analyzer.\n";
082    }
083
084    /** Check for validity of this strategy.
085     *
086     *  @return True since this strategy is always valid.
087     */
088    @Override
089    public boolean valid() {
090        return true;
091    }
092
093    ///////////////////////////////////////////////////////////////////
094    ////                         protected methods                 ////
095
096    /** Compute the self-loop edges in the graph in the form of
097     *  a collection. Each element of the collection is an {@link Edge}.
098     *
099     *  @return The self-loop edges.
100     */
101    @Override
102    protected Object _compute() {
103        ArrayList selfLoopEdges = new ArrayList();
104        Iterator edges = graph().edges().iterator();
105
106        while (edges.hasNext()) {
107            Edge edge = (Edge) edges.next();
108
109            if (edge.isSelfLoop()) {
110                selfLoopEdges.add(edge);
111            }
112        }
113
114        return selfLoopEdges;
115    }
116
117    /** Return the result of this analysis (collection of self-loop edges)
118     *  in a form that cannot be modified.
119     *
120     *  @return The analysis result in unmodifiable form.
121     */
122    protected Object _convertResult() {
123        return Collections.unmodifiableList((List) _result());
124    }
125}