What's your time zone?

JAVA日期和時(shí)間類徹底解決（1）

你是否在苦苦掙扎在JAVA語言中的日期和時(shí)間中？當(dāng)你在計(jì)算機(jī)上顯示日期和時(shí)間時(shí)，, 是否要快一個(gè)小時(shí)？或者可能要早一個(gè)小時(shí)？, 或者兩個(gè)小時(shí), 或者更嚴(yán)重？ 當(dāng)你試圖用JAVA寫日期和時(shí)間到一個(gè)文件中，或者到你的數(shù)據(jù)庫中(通過Java Database Connectivity (JDBC))— 錯(cuò)誤的時(shí)間被保存了嗎？

我曾經(jīng)被這個(gè)問題困饒過很長時(shí)間。我不能解決為什么JAVA改變了我給的時(shí)間戳（timestamps）。我從數(shù)據(jù)庫中檢索時(shí)間戳數(shù)據(jù)并顯示在我的圖形用戶接口(GUI)中時(shí), 總是會(huì)顯示一個(gè)不同的時(shí)間—和我期望的值要相差1，2或3個(gè)小時(shí)。我重新檢查了數(shù)據(jù)庫中的值，它是正常的。 那么到底應(yīng)該怎么辦呢？

調(diào)查 
最終我決定對這種情況來調(diào)查一番。首先，我寫了一個(gè)簡單的JAVA類:

import java.util.*;

public class DateTest {
  public static void main(String[] args) {
    System.out.println("Date = " + new Date());
    System.out.println("Calendar = " + Calendar.getInstance());
  }
}


在Windows 98 的 Java 2 Platform, Standard Edition (J2SE) 1.3.1_01,，我得到：

Date = Tue May 06 08:13:17 IDT 2003
Calendar = java.util.GregorianCalendar[time=1052197997184,areFieldsSet=true,areAllFieldsSet
=true,lenient=false,zone=java.util.SimpleTimeZone[id=Asia/Jerusalem,offset=7200000,
dstSavings=3600000,useDaylight=true,startYear=0,startMode=1,startMonth=3,startDay=9,
startDayOfWeek=0,startTime=3600000,startTimeMode=0,endMode=1,endMonth=8,endDay=24,
endDayOfWeek=0,endTime=3600000,endTimeMode=0],firstDayOfWeek=1,minimalDaysInFirstWeek=1,
ERA=1,YEAR=2003,MONTH=4,WEEK_OF_YEAR=19,WEEK_OF_MONTH=2,DAY_OF_MONTH=6,DAY_OF_YEAR=126,
DAY_OF_WEEK=3,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=8,HOUR_OF_DAY=8,MINUTE=13,SECOND=17,
MILLISECOND=184,ZONE_OFFSET=7200000,DST_OFFSET=3600000]


在Sun Solaris 7 with J2SE 1.3.1_02，我得到：

Date = Tue May 06 08:13:17 IDT 2003
Calendar = java.util.GregorianCalendar[time=1052197997184,areFieldsSet=true,areAllFieldsSet
=true,lenient=false,zone=java.util.SimpleTimeZone[id=Asia/Jerusalem,offset=7200000,
dstSavings=3600000,useDaylight=true,startYear=0,startMode=1,startMonth=3,startDay=9,
startDayOfWeek=0,startTime=3600000,startTimeMode=0,endMode=1,endMonth=8,endDay=24,
endDayOfWeek=0,endTime=3600000,endTimeMode=0],firstDayOfWeek=1,minimalDaysInFirstWeek=1,
ERA=1,YEAR=2003,MONTH=4,WEEK_OF_YEAR=19,WEEK_OF_MONTH=2,DAY_OF_MONTH=6,DAY_OF_YEAR=126,
DAY_OF_WEEK=3,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=8,HOUR_OF_DAY=8,MINUTE=13,SECOND=17,
MILLISECOND=184,ZONE_OFFSET=7200000,DST_OFFSET=3600000]


在 Linux Mandrake 7.2 with J2SE 1.3.0, 我得到：

Date = Mon May 05 21:04:32 GMT+00:00 2003
Calendar = java.util.GregorianCalendar[time=1052168673155,areFieldsSet=true,areAllFieldsSet
=true,lenient=true,zone=java.util.SimpleTimeZone[id=Custom,offset=0,dstSavings=3600000,
useDaylight=false,startYear=0,startMode=0,startMonth=0,startDay=0,startDayOfWeek=0,
startTime=0,startTimeMode=0,endMode=0,endMonth=0,endDay=0,endDayOfWeek=0,endTime=0,
endTimeMode=0],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2003,MONTH=4,
WEEK_OF_YEAR=19,WEEK_OF_MONTH=2,DAY_OF_MONTH=5,DAY_OF_YEAR=125,DAY_OF_WEEK=2,
DAY_OF_WEEK_IN_MONTH=1,AM_PM=1,HOUR=9,HOUR_OF_DAY=21,MINUTE=4,SECOND=33,MILLISECOND=155,
ZONE_OFFSET=0,DST_OFFSET=0]