001    /*
002     *  Copyright 2001-2009 Stephen Colebourne
003     *
004     *  Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
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.joda.time.tz;
017    
018    import java.util.Collections;
019    import java.util.Set;
020    
021    import org.joda.time.DateTimeZone;
022    
023    /**
024     * Simple time zone provider that supports only UTC.
025     * <p>
026     * UTCProvider is thread-safe and immutable.
027     *
028     * @author Brian S O'Neill
029     * @since 1.0
030     */
031    public final class UTCProvider implements Provider {
032    
033        /**
034         * Constructor.
035         */
036        public UTCProvider() {
037            super();
038        }
039    
040        /**
041         * Returns {@link DateTimeZone#UTC UTC} for <code>"UTC"</code>, null
042         * otherwise.
043         */
044        public DateTimeZone getZone(String id) {
045            if ("UTC".equalsIgnoreCase(id)) {
046                return DateTimeZone.UTC;
047            }
048            return null;
049        }
050    
051        /**
052         * Returns a singleton collection containing only <code>"UTC"</code>.
053         */    
054        public Set<String> getAvailableIDs() {
055            return Collections.singleton("UTC");
056        }
057    
058    }