code: /*
   * 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
   * 
   *      http://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.lang.time;
  
  import java.util.Date;
  import java.util.Locale;
  import java.util.TimeZone;
  
  /**
   * <p>Date and time formatting utilities and constants.</p>
   *
   * <p>Formatting is performed using the
   * {@link org.apache.commons.lang.time.FastDateFormat} class.</p>
   *
   * @author Apache Ant - DateUtils
   * @author <a href="mailto:sbailliez@apache.org">Stephane Bailliez</a>
   * @author <a href="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a>
   * @author Stephen Colebourne
   * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a>
   * @since 2.0
   * @version $Id: DateFormatUtils.java 437554 2006-08-28 06:21:41Z bayard $
   */
  public class DateFormatUtils {
  
      /**
       * ISO8601 formatter for date-time without time zone.
       * The format used is <tt>yyyy-MM-dd'T'HH:mm:ss</tt>.
       */
      public static final FastDateFormat ISO_DATETIME_FORMAT
              = FastDateFormat.getInstance("yyyy-MM-dd'T'HH:mm:ss");
  
      /**
       * ISO8601 formatter for date-time with time zone.
       * The format used is <tt>yyyy-MM-dd'T'HH:mm:ssZZ</tt>.
       */
      public static final FastDateFormat ISO_DATETIME_TIME_ZONE_FORMAT
              = FastDateFormat.getInstance("yyyy-MM-dd'T'HH:mm:ssZZ");
  
      /**
       * ISO8601 formatter for date without time zone.
       * The format used is <tt>yyyy-MM-dd</tt>.
       */
      public static final FastDateFormat ISO_DATE_FORMAT
              = FastDateFormat.getInstance("yyyy-MM-dd");
  
      /**
       * ISO8601-like formatter for date with time zone.
       * The format used is <tt>yyyy-MM-ddZZ</tt>.
       * This pattern does not comply with the formal ISO8601 specification
       * as the standard does not allow a time zone  without a time.
       */
      public static final FastDateFormat ISO_DATE_TIME_ZONE_FORMAT
              = FastDateFormat.getInstance("yyyy-MM-ddZZ");
  
      /**
       * ISO8601 formatter for time without time zone.
       * The format used is <tt>'T'HH:mm:ss</tt>.
       */
      public static final FastDateFormat ISO_TIME_FORMAT
              = FastDateFormat.getInstance("'T'HH:mm:ss");
  
      /**
       * ISO8601 formatter for time with time zone.
       * The format used is <tt>'T'HH:mm:ssZZ</tt>.
       */
      public static final FastDateFormat ISO_TIME_TIME_ZONE_FORMAT
              = FastDateFormat.getInstance("'T'HH:mm:ssZZ");
  
      /**
       * ISO8601-like formatter for time without time zone.
       * The format used is <tt>HH:mm:ss</tt>.
       * This pattern does not comply with the formal ISO8601 specification
       * as the standard requires the 'T' prefix for times.
       */
      public static final FastDateFormat ISO_TIME_NO_T_FORMAT
              = FastDateFormat.getInstance("HH:mm:ss");
  
      /**
       * ISO8601-like formatter for time with time zone.
       * The format used is <tt>HH:mm:ssZZ</tt>.
       * This pattern does not comply with the formal ISO8601 specification
       * as the standard requires the 'T' prefix for times.
       */
      public static final FastDateFormat ISO_TIME_NO_T_TIME_ZONE_FORMAT
              = FastDateFormat.getInstance("HH:mm:ssZZ");
  
      /**
       * SMTP (and probably other) date headers.
       * The format used is <tt>EEE, dd MMM yyyy HH:mm:ss Z</tt> in US locale.
       */
      public static final FastDateFormat SMTP_DATETIME_FORMAT
              = FastDateFormat.getInstance("EEE, dd MMM yyyy HH:mm:ss Z", Locale.US);
  
      //-----------------------------------------------------------------------
      /**
       * <p>DateFormatUtils instances should NOT be constructed in standard programming.</p>
       *
       * <p>This constructor is public to permit tools that require a JavaBean instance
       * to operate.</p>
       */
      public DateFormatUtils() {
          super();
      }
  
      /**
       * <p>Formats a date/time into a specific pattern using the UTC time zone.</p>
       * 
       * @param millis  the date to format expressed in milliseconds
       * @param pattern  the pattern to use to format the date
       * @return the formatted date
       */
      public static String formatUTC(long millis, String pattern) {
          return format(new Date(millis), pattern, DateUtils.UTC_TIME_ZONE, null);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern using the UTC time zone.</p>
       * 
       * @param date  the date to format
       * @param pattern  the pattern to use to format the date
       * @return the formatted date
       */
      public static String formatUTC(Date date, String pattern) {
          return format(date, pattern, DateUtils.UTC_TIME_ZONE, null);
      }
      
      /**
       * <p>Formats a date/time into a specific pattern using the UTC time zone.</p>
       * 
       * @param millis  the date to format expressed in milliseconds
       * @param pattern  the pattern to use to format the date
       * @param locale  the locale to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String formatUTC(long millis, String pattern, Locale locale) {
          return format(new Date(millis), pattern, DateUtils.UTC_TIME_ZONE, locale);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern using the UTC time zone.</p>
       * 
       * @param date  the date to format
       * @param pattern  the pattern to use to format the date
       * @param locale  the locale to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String formatUTC(Date date, String pattern, Locale locale) {
          return format(date, pattern, DateUtils.UTC_TIME_ZONE, locale);
      }
      
      /**
       * <p>Formats a date/time into a specific pattern.</p>
       * 
       * @param millis  the date to format expressed in milliseconds
       * @param pattern  the pattern to use to format the date
       * @return the formatted date
       */
      public static String format(long millis, String pattern) {
          return format(new Date(millis), pattern, null, null);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern.</p>
       * 
       * @param date  the date to format
       * @param pattern  the pattern to use to format the date
       * @return the formatted date
       */
      public static String format(Date date, String pattern) {
          return format(date, pattern, null, null);
      }
      
      /**
       * <p>Formats a date/time into a specific pattern in a time zone.</p>
       * 
       * @param millis  the time expressed in milliseconds
       * @param pattern  the pattern to use to format the date
       * @param timeZone  the time zone  to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String format(long millis, String pattern, TimeZone timeZone) {
          return format(new Date(millis), pattern, timeZone, null);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern in a time zone.</p>
       * 
       * @param date  the date to format
       * @param pattern  the pattern to use to format the date
       * @param timeZone  the time zone  to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String format(Date date, String pattern, TimeZone timeZone) {
          return format(date, pattern, timeZone, null);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern in a locale.</p>
       * 
       * @param millis  the date to format expressed in milliseconds
       * @param pattern  the pattern to use to format the date
       * @param locale  the locale to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String format(long millis, String pattern, Locale locale) {
          return format(new Date(millis), pattern, null, locale);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern in a locale.</p>
       * 
       * @param date  the date to format
       * @param pattern  the pattern to use to format the date
       * @param locale  the locale to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String format(Date date, String pattern, Locale locale) {
          return format(date, pattern, null, locale);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern in a time zone  and locale.</p>
       * 
       * @param millis  the date to format expressed in milliseconds
       * @param pattern  the pattern to use to format the date
       * @param timeZone  the time zone  to use, may be <code>null</code>
       * @param locale  the locale to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String format(long millis, String pattern, TimeZone timeZone, Locale locale) {
          return format(new Date(millis), pattern, timeZone, locale);
      }
  
      /**
       * <p>Formats a date/time into a specific pattern in a time zone  and locale.</p>
       * 
       * @param date  the date to format
       * @param pattern  the pattern to use to format the date
       * @param timeZone  the time zone  to use, may be <code>null</code>
       * @param locale  the locale to use, may be <code>null</code>
       * @return the formatted date
       */
      public static String format(Date date, String pattern, TimeZone timeZone, Locale locale) {
          FastDateFormat df = FastDateFormat.getInstance(pattern, timeZone, locale);
          return df.format(date);
      }
  
  }
  