001    /*
002     * Copyright (c) 2005 Einar Pehrson <einar@pehrson.nu>.
003     *
004     * This file is part of
005     * CleanSheets - a spreadsheet application for the Java platform.
006     *
007     * CleanSheets is free software; you can redistribute it and/or modify
008     * it under the terms of the GNU General Public License as published by
009     * the Free Software Foundation; either version 2 of the License, or
010     * (at your option) any later version.
011     *
012     * CleanSheets is distributed in the hope that it will be useful,
013     * but WITHOUT ANY WARRANTY; without even the implied warranty of
014     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
015     * GNU General Public License for more details.
016     *
017     * You should have received a copy of the GNU General Public License
018     * along with CleanSheets; if not, write to the Free Software
019     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
020     */
021    package csheets.core.formula.util;
022    
023    import java.util.SortedSet;
024    import java.util.TreeSet;
025    
026    import csheets.core.formula.Expression;
027    import csheets.core.formula.Reference;
028    
029    /**
030     * An expression visitor that collects the references from an expression.
031     * @author Einar Pehrson
032     */
033    public class ReferenceFetcher extends AbstractExpressionVisitor {
034    
035            /** The references that have been fetched */
036            private SortedSet<Reference> references;
037    
038            /**
039             * Creates a new reference fetcher.
040             */
041            public ReferenceFetcher() {}
042    
043            /**
044             * Traverses the given expression and returns the references that were found.
045             * @param expression the expression from which to fetch references
046             * @return the references that have been fetched
047             */
048            public SortedSet<Reference> getReferences(Expression expression) {
049                    references = new TreeSet<Reference>();
050                    expression.accept(this);
051                    return references;
052            }
053    
054            /**
055             * Adds the reference to the set.
056             * @param reference the reference to visit
057             */
058            public Object visitReference(Reference reference) {
059                    references.add(reference);
060                    return reference;
061            }
062    }