src/main/java/org/apache/commons/lang3/time/TimeZones.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.lang3.time;

import java.time.ZoneId;
import java.util.TimeZone;

import org.apache.commons.lang3.ArraySorter;
import org.apache.commons.lang3.JavaVersion;
import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.lang3.SystemProperties;
import org.apache.commons.lang3.SystemUtils;

/**
 * Helps dealing with {@link java.util.TimeZone}s.
 *
 * @since 3.7
 */
public class TimeZones {

    /**
     * A public version of {@link java.util.TimeZone}'s package private {@code GMT_ID} field.
     */
    public static final String GMT_ID = "GMT";

    /**
     * The GMT time zone.
     *
     * @since 3.13.0
     */
    public static final TimeZone GMT = TimeZones.getTimeZone(GMT_ID);

    private static final boolean JAVA_25 = SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_25);

    /**
     * The sorted available IDs.
     * <p>
     * Make a defensive copy, just in case.
     * </p>
     * @see TimeZone#getAvailableIDs()
     */
    static final String[] SORTED_AVAILABLE_IDS = ArraySorter.sort(TimeZone.getAvailableIDs().clone());

    /**
     * Delegates to {@link TimeZone#getTimeZone(String)}, on Java 25 and up, maps an ID if it's a key in {@link ZoneId#SHORT_IDS}.
     * <p>
     * On Java 25, calling {@link TimeZone#getTimeZone(String)} with an ID in {@link ZoneId#SHORT_IDS} writes a message to {@link System#err} in the form:
     * </p>
     *
     * <pre>
     * WARNING: Use of the three-letter time zone ID "the-short-id" is deprecated and it will be removed in a future release
     * </pre>
     * <p>
     * You can disable mapping from {@link ZoneId#SHORT_IDS} by setting the system property {@code "TimeZones.mapShortIDs=false"}.
     * </p>
     *
     * @param id Same as {@link TimeZone#getTimeZone(String)}.
     * @return Same as {@link TimeZone#getTimeZone(String)}.
     * @since 3.20.0
     */
    public static TimeZone getTimeZone(final String id) {
        return TimeZone.getTimeZone(JAVA_25 && mapShortIDs() ? ZoneId.SHORT_IDS.getOrDefault(id, id) : id);
    }

    private static boolean mapShortIDs() {
        return SystemProperties.getBoolean(TimeZones.class, "mapShortIDs", () -> true);
    }

    /**
     * Returns the given TimeZone if non-{@code null}, otherwise {@link TimeZone#getDefault()}.
     *
     * @param timeZone a locale or {@code null}.
     * @return the given locale if non-{@code null}, otherwise {@link TimeZone#getDefault()}.
     * @since 3.13.0
     */
    public static TimeZone toTimeZone(final TimeZone timeZone) {
        return ObjectUtils.getIfNull(timeZone, TimeZone::getDefault);
    }

    /** Do not instantiate. */
    private TimeZones() {
    }
}