LabeledEnum


1   /*
2    * Copyright 2002-2006 the original author or authors.
3    *
4    * Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
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  
17  package org.springframework.core.enums;
18  
19  import java.io.Serializable  ;
20  import java.util.Comparator  ;
21  
22  import org.springframework.util.comparator.CompoundComparator;
23  import org.springframework.util.comparator.NullSafeComparator;
24  
25  /**
26   * A interface for objects that represent a labled enumeration.
27   * Each such enum instance has the following characteristics:
28   *
29   * <ul>
30   * <li>A type that identifies the enum's class.
31   * For example: <code>com.mycompany.util.FileFormat</code>.
32   *
33   * <li>A code that uniquely identifies the enum within the context of its type.
34   * For example: "CSV". Different classes of codes are possible
35   * (Character, Integer, String).
36   *
37   * <li>A descriptive label. For example: "the CSV File Format".
38   * </ul>
39   *
40   * @author Keith Donald
41   * @since 1.2.2
42   */
43  public interface LabeledEnum extends Comparable  , Serializable   {
44  
45      /**
46       * Return this enumeration's type.
47       */
48      Class   getType();
49  
50      /**
51       * Return this enumeration's code.
52       * <p>Each code should be unique within enumeration's of the same type.
53       */
54      Comparable   getCode();
55  
56      /**
57       * Return a descriptive, optional label.
58       */
59      String   getLabel();
60  
61  
62      // Constants for standard enum ordering (Comparator implementations)
63  
64      /**
65       * Shared Comparator instance that sorts enumerations by <code>CODE_ORDER</code>.
66       */
67      Comparator   CODE_ORDER = new Comparator  () {
68          public int compare(Object   o1, Object   o2) {
69              Comparable   c1 = ((LabeledEnum) o1).getCode();
70              Comparable   c2 = ((LabeledEnum) o2).getCode();
71              return c1.compareTo(c2);
72          }
73      };
74  
75      /**
76       * Shared Comparator instance that sorts enumerations by <code>LABEL_ORDER</code>.
77       */
78      Comparator   LABEL_ORDER = new Comparator  () {
79          public int compare(Object   o1, Object   o2) {
80              LabeledEnum e1 = (LabeledEnum) o1;
81              LabeledEnum e2 = (LabeledEnum) o2;
82              Comparator   comp = new NullSafeComparator(String.CASE_INSENSITIVE_ORDER, true);
83              return comp.compare(e1.getLabel(), e2.getLabel());
84          }
85      };
86  
87      /**
88       * Shared Comparator instance that sorts enumerations by <code>LABEL_ORDER</code>,
89       * then <code>CODE_ORDER</code>.
90       */
91      Comparator   DEFAULT_ORDER =
92              new CompoundComparator(new Comparator  [] { LABEL_ORDER, CODE_ORDER });
93  
94  }
95
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