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1   /*
2    *  Copyright 2001-2009 Stephen Colebourne
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  package org.joda.time.tz;
17  
18  import java.util.Collections;
19  import java.util.Set;
20  
21  import org.joda.time.DateTimeZone;
22  
23  /**
24   * Simple time zone provider that supports only UTC.
25   * <p>
26   * UTCProvider is thread-safe and immutable.
27   *
28   * @author Brian S O'Neill
29   * @since 1.0
30   */
31  public final class UTCProvider implements Provider {
32  
33      /**
34       * Constructor.
35       */
36      public UTCProvider() {
37          super();
38      }
39  
40      /**
41       * Returns {@link DateTimeZone#UTC UTC} for <code>"UTC"</code>, null
42       * otherwise.
43       */
44      public DateTimeZone getZone(String id) {
45          if ("UTC".equalsIgnoreCase(id)) {
46              return DateTimeZone.UTC;
47          }
48          return null;
49      }
50  
51      /**
52       * Returns a singleton collection containing only <code>"UTC"</code>.
53       */    
54      public Set<String> getAvailableIDs() {
55          return Collections.singleton("UTC");
56      }
57  
58  }