001    /*
002     $Id: OrderBy.java,v 1.1 2003/10/09 17:24:19 jstrachan Exp $
003    
004     Copyright 2003 (C) James Strachan and Bob Mcwhirter. All Rights Reserved.
005    
006     Redistribution and use of this software and associated documentation
007     ("Software"), with or without modification, are permitted provided
008     that the following conditions are met:
009    
010     1. Redistributions of source code must retain copyright
011        statements and notices.  Redistributions must also contain a
012        copy of this document.
013    
014     2. Redistributions in binary form must reproduce the
015        above copyright notice, this list of conditions and the
016        following disclaimer in the documentation and/or other
017        materials provided with the distribution.
018    
019     3. The name "groovy" must not be used to endorse or promote
020        products derived from this Software without prior written
021        permission of The Codehaus.  For written permission,
022        please contact info@codehaus.org.
023    
024     4. Products derived from this Software may not be called "groovy"
025        nor may "groovy" appear in their names without prior written
026        permission of The Codehaus. "groovy" is a registered
027        trademark of The Codehaus.
028    
029     5. Due credit should be given to The Codehaus -
030        http://groovy.codehaus.org/
031    
032     THIS SOFTWARE IS PROVIDED BY THE CODEHAUS AND CONTRIBUTORS
033     ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
034     NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
035     FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
036     THE CODEHAUS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
037     INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
038     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
039     SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
040     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
041     STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
042     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
043     OF THE POSSIBILITY OF SUCH DAMAGE.
044    
045     */
046    package groovy.util;
047    
048    import groovy.lang.Closure;
049    
050    import java.util.ArrayList;
051    import java.util.Comparator;
052    import java.util.Iterator;
053    import java.util.List;
054    
055    /**
056     * A helper class for sorting objects via a closure to return the field
057     * or operation on which to sort.
058     * 
059     * @author <a href="mailto:james@coredevelopers.net">James Strachan</a>
060     * @version $Revision: 1.1 $
061     */
062    public class OrderBy implements Comparator {
063    
064        List closures;
065    
066        public OrderBy() {
067            this.closures = new ArrayList();
068        }
069    
070        public OrderBy(Closure closure) {
071            this();
072            closures.add(closure);
073        }
074    
075        public OrderBy(List closures) {
076            this.closures = closures;
077        }
078    
079        public void add(Closure closure) {
080            closures.add(closure);
081        }
082    
083        public int compare(Object object1, Object object2) {
084            for (Iterator iter = closures.iterator(); iter.hasNext();) {
085                Closure closure = (Closure) iter.next();
086                Object value1 = closure.call(object1);
087                Object value2 = closure.call(object2);
088    
089                if (value1 == value2) {
090                    continue;
091                }
092                if (value1 == null) {
093                    return -1;
094                }
095                if (value1 instanceof Comparable) {
096                    Comparable c1 = (Comparable) value1;
097                    return c1.compareTo(value2);
098                }
099                if (value1.equals(value2)) {
100                    continue;
101                }
102                return value1.hashCode() - value2.hashCode();
103            }
104            return 0;
105        }
106    }