EvaluationResultCacheComparator


1   /*******************************************************************************
2    * Copyright (c) 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   ******************************************************************************/
11  
12  package org.eclipse.ui.internal.services;
13  
14  import java.util.Comparator  ;
15  
16  import org.eclipse.ui.internal.util.Util;
17  
18  /**
19   * <p>
20   * Compares two evaluation result caches ({@link IEvaluationResultCache}). The
21   * cache with the lowest source priority is considered "greater". In the event
22   * of a tie, other characteristics are checked.
23   * </p>
24   * <p>
25   * This class is only intended for use within the
26   * <code>org.eclipse.ui.workbench</code> plug-in.
27   * </p>
28   * 
29   * @since 3.2
30   * 
31   */
32  public final class EvaluationResultCacheComparator implements Comparator   {
33  
34      public final int compare(final Object   object1, final Object   object2) {
35          if (Util.equals(object2, object1)) {
36              return 0;
37          }
38  
39          final IEvaluationResultCache cache1 = (IEvaluationResultCache) object1;
40          final IEvaluationResultCache cache2 = (IEvaluationResultCache) object2;
41          int comparison;
42  
43          /*
44           * Note: all of the comparisons are flipped intentionally. This allows
45           * those items with greater values to appear earlier when using an
46           * iterator.
47           */
48          // if objects went to the trouble to implement Comparable
49          // we should use it ... this algorithm can accept a natural ordering
50          // that's not compatible with equals.
51          if (object1 instanceof Comparable   && object2 instanceof Comparable  ) {
52              comparison = Util.compare((Comparable  ) object2,
53                      (Comparable  ) object1);
54              if (comparison != 0) {
55                  return comparison;
56              }
57          }
58  
59          return Util.compareIdentity(cache2, cache1);
60      }
61  }
62  
63
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