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 */
016package org.joda.time.tz;
017
018import java.util.Collections;
019import java.util.Set;
020import 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 */
030public 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}