    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.lang3.time;
    018
    019import java.util.TimeZone;
    020import java.util.regex.Matcher;
    021import java.util.regex.Pattern;
    022
    023/**
    024 * Faster methods to produce custom time zones.
    025 *
    026 * @since 3.7
    027 */
    028public class FastTimeZone {
    029
    030    private static final Pattern GMT_PATTERN = Pattern.compile("^(?:(?i)GMT)?([+-])?(\\d\\d?)?(:?(\\d\\d?))?$");
    031
    032    private static final TimeZone GREENWICH = new GmtTimeZone(false, 0, 0);
    033
    034    /**
    035     * Gets the GMT TimeZone.
    036     * @return A TimeZone with a raw offset of zero.
    037     */
    038    public static TimeZone getGmtTimeZone() {
    039        return GREENWICH;
    040    }
    041
    042    /**
    043     * Gets a TimeZone with GMT offsets.  A GMT offset must be either 'Z', or 'UTC', or match
    044     * <em>(GMT)? hh?(:?mm?)?</em>, where h and m are digits representing hours and minutes.
    045     *
    046     * @param pattern The GMT offset
    047     * @return A TimeZone with offset from GMT or null, if pattern does not match.
    048     */
    049    public static TimeZone getGmtTimeZone(final String pattern) {
    050        if ("Z".equals(pattern) || "UTC".equals(pattern)) {
    051            return GREENWICH;
    052        }
    053
    054        final Matcher m = GMT_PATTERN.matcher(pattern);
    055        if (m.matches()) {
    056            final int hours = parseInt(m.group(2));
    057            final int minutes = parseInt(m.group(4));
    058            if (hours == 0 && minutes == 0) {
    059                return GREENWICH;
    060            }
    061            return new GmtTimeZone(parseSign(m.group(1)), hours, minutes);
    062        }
    063        return null;
    064    }
    065
    066    /**
    067     * Gets a TimeZone, looking first for GMT custom ids, then falling back to Olson ids.
    068     * A GMT custom id can be 'Z', or 'UTC', or has an optional prefix of GMT,
    069     * followed by sign, hours digit(s), optional colon(':'), and optional minutes digits.
    070     * i.e. <em>[GMT] (+|-) Hours [[:] Minutes]</em>
    071     *
    072     * @param id A GMT custom id (or Olson id
    073     * @return A timezone
    074     */
    075    public static TimeZone getTimeZone(final String id) {
    076        final TimeZone tz = getGmtTimeZone(id);
    077        if (tz != null) {
    078            return tz;
    079        }
    080        return TimeZone.getTimeZone(id);
    081    }
    082
    083    private static int parseInt(final String group) {
    084        return group != null ? Integer.parseInt(group) : 0;
    085    }
    086
    087    private static boolean parseSign(final String group) {
    088        return group != null && group.charAt(0) == '-';
    089    }
    090
    091    // do not instantiate
    092    private FastTimeZone() {
    093    }
    094
    095}