001    /*
002     *  Copyright 2001-2005 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    import org.joda.time.DateTimeZone;
021    
022    /**
023     * Simple time zone provider that supports only UTC.
024     * <p>
025     * UTCProvider is thread-safe and immutable.
026     *
027     * @author Brian S O'Neill
028     * @since 1.0
029     */
030    public final class UTCProvider implements Provider {
031    
032        /**
033         * Constructor.
034         */
035        public UTCProvider() {
036            super();
037        }
038    
039        /**
040         * Returns {@link DateTimeZone#UTC UTC} for <code>"UTC"</code>, null
041         * otherwise.
042         */
043        public DateTimeZone getZone(String id) {
044            if ("UTC".equalsIgnoreCase(id)) {
045                return DateTimeZone.UTC;
046            }
047            return null;
048        }
049    
050        /**
051         * Returns a singleton collection containing only <code>"UTC"</code>.
052         */    
053        public Set getAvailableIDs() {
054            return Collections.singleton("UTC");
055        }
056    
057    }