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1   /**
2    * Copyright 2005-2014 The Kuali Foundation
3    *
4    * Licensed under the Educational Community License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.opensource.org/licenses/ecl2.php
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.kuali.rice.kns.web.comparator;
17  
18  import java.io.Serializable;
19  import java.util.Comparator;
20  
21  public class NullValueComparator implements Comparator, Serializable {
22      private static final NullValueComparator theInstance = new NullValueComparator();
23      
24      public NullValueComparator() {
25      }
26  
27      public static NullValueComparator getInstance() {
28          return theInstance;
29      }
30      
31      public int compare(Object o1, Object o2) {
32          if (o1 == null && o2 == null) {
33              return 0;
34          }
35          if (o1 == null) {
36              return -1;
37          }
38          else if (o2 == null) {
39              return 1;
40          }
41          else {
42              // probably won't go into this code segment, but doing it just in case
43              return CellComparatorHelper.getAppropriateValueComparatorForPropertyClass(o1.getClass()).compare(o1, o2);
44          }
45      }
46  }