Java日期处理工具类

/*   * 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.ftpserver.util;    import java.text.DateFormat;  import java.text.ParseException;  import java.text.SimpleDateFormat;  import java.util.Calendar;  import java.util.Date;  import java.util.GregorianCalendar;  import java.util.TimeZone;    /**   * <strong>Internal class, do not use directly.</strong>   *    * Standard date related utility methods.   *   * @author <a href="http://mina.apache.org">Apache MINA Project</a>   */  public class DateUtils {        private static final TimeZone TIME_ZONE_UTC = TimeZone.getTimeZone("UTC");        private final static String[] MONTHS = { "Jan", "Feb", "Mar", "Apr", "May",              "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };        /*       * Creates the DateFormat object used to parse/format       * dates in FTP format.       */      private static final ThreadLocal<DateFormat> FTP_DATE_FORMAT = new ThreadLocal<DateFormat>() {            @Override          protected DateFormat initialValue() {              DateFormat df=new SimpleDateFormat("yyyyMMddHHmmss");              df.setLenient(false);              df.setTimeZone(TimeZone.getTimeZone("GMT"));              return df;          }                };            /**       * Get unix style date string.       */      public final static String getUnixDate(long millis) {          if (millis < 0) {              return "------------";          }            StringBuffer sb = new StringBuffer(16);          Calendar cal = new GregorianCalendar();          cal.setTimeInMillis(millis);            // month          sb.append(MONTHS[cal.get(Calendar.MONTH)]);          sb.append(' ');            // day          int day = cal.get(Calendar.DATE);          if (day < 10) {              sb.append(' ');          }          sb.append(day);          sb.append(' ');            long sixMonth = 15811200000L; // 183L * 24L * 60L * 60L * 1000L;          long nowTime = System.currentTimeMillis();          if (Math.abs(nowTime - millis) > sixMonth) {                // year              int year = cal.get(Calendar.YEAR);              sb.append(' ');              sb.append(year);          } else {                // hour              int hh = cal.get(Calendar.HOUR_OF_DAY);              if (hh < 10) {                  sb.append('0');              }              sb.append(hh);              sb.append(':');                // minute              int mm = cal.get(Calendar.MINUTE);              if (mm < 10) {                  sb.append('0');              }              sb.append(mm);          }          return sb.toString();      }        /**       * Get ISO 8601 timestamp.       */      public final static String getISO8601Date(long millis) {          StringBuffer sb = new StringBuffer(19);          Calendar cal = new GregorianCalendar();          cal.setTimeInMillis(millis);            // year          sb.append(cal.get(Calendar.YEAR));            // month          sb.append('-');          int month = cal.get(Calendar.MONTH) + 1;          if (month < 10) {              sb.append('0');          }          sb.append(month);            // date          sb.append('-');          int date = cal.get(Calendar.DATE);          if (date < 10) {              sb.append('0');          }          sb.append(date);            // hour          sb.append('T');          int hour = cal.get(Calendar.HOUR_OF_DAY);          if (hour < 10) {              sb.append('0');          }          sb.append(hour);            // minute          sb.append(':');          int min = cal.get(Calendar.MINUTE);          if (min < 10) {              sb.append('0');          }          sb.append(min);            // second          sb.append(':');          int sec = cal.get(Calendar.SECOND);          if (sec < 10) {              sb.append('0');          }          sb.append(sec);            return sb.toString();      }        /**       * Get FTP date.       */      public final static String getFtpDate(long millis) {          StringBuffer sb = new StringBuffer(20);                    // MLST should use UTC          Calendar cal = new GregorianCalendar(TIME_ZONE_UTC);          cal.setTimeInMillis(millis);                      // year          sb.append(cal.get(Calendar.YEAR));            // month          int month = cal.get(Calendar.MONTH) + 1;          if (month < 10) {              sb.append('0');          }          sb.append(month);            // date          int date = cal.get(Calendar.DATE);          if (date < 10) {              sb.append('0');          }          sb.append(date);            // hour          int hour = cal.get(Calendar.HOUR_OF_DAY);          if (hour < 10) {              sb.append('0');          }          sb.append(hour);            // minute          int min = cal.get(Calendar.MINUTE);          if (min < 10) {              sb.append('0');          }          sb.append(min);            // second          int sec = cal.get(Calendar.SECOND);          if (sec < 10) {              sb.append('0');          }          sb.append(sec);            // millisecond          sb.append('.');          int milli = cal.get(Calendar.MILLISECOND);          if (milli < 100) {              sb.append('0');          }          if (milli < 10) {              sb.append('0');          }          sb.append(milli);          return sb.toString();      }      /*       *  Parses a date in the format used by the FTP commands        *  involving dates(MFMT, MDTM)       */      public final static Date parseFTPDate(String dateStr) throws ParseException{          return FTP_DATE_FORMAT.get().parse(dateStr);                }        }