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 */
021package csheets.core.formula.util;
022
023import java.util.SortedSet;
024import java.util.TreeSet;
025
026import csheets.core.formula.Expression;
027import csheets.core.formula.Reference;
028
029/**
030 * An expression visitor that collects the references from an expression.
031 * @author Einar Pehrson
032 */
033public 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}