001    /**
002     * Copyright 2005-2012 The Kuali Foundation
003     *
004     * Licensed under the Educational Community License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.opensource.org/licenses/ecl2.php
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package org.kuali.rice.kns.web.comparator;
017    
018    import java.io.Serializable;
019    import java.util.Comparator;
020    
021    public class NullValueComparator implements Comparator, Serializable {
022        private static final NullValueComparator theInstance = new NullValueComparator();
023        
024        public NullValueComparator() {
025        }
026    
027        public static NullValueComparator getInstance() {
028            return theInstance;
029        }
030        
031        public int compare(Object o1, Object o2) {
032            if (o1 == null && o2 == null) {
033                return 0;
034            }
035            if (o1 == null) {
036                return -1;
037            }
038            else if (o2 == null) {
039                return 1;
040            }
041            else {
042                // probably won't go into this code segment, but doing it just in case
043                return CellComparatorHelper.getAppropriateValueComparatorForPropertyClass(o1.getClass()).compare(o1, o2);
044            }
045        }
046    }