java - Java时区在运行时更改

我的Java程序需要使用当前本地时区记录事件。问题是，用户可以更改时区，但是即使系统时区已更改，Java程序仍会以“旧”时区运行。

我怀疑Java虚拟机在运行Java程序时将时区设置为默认时区(Timezone.setDefault()的javadoc说“将默认值重置为虚拟机首次启动时的原始值。”)

真的吗？ Java无法将默认时区更新为新的系统时区，因此需要重启VM？

最佳答案

while (true) {
    Thread.sleep(1000);
    System.out.println(TimeZone.getDefault());
    System.getProperties().setProperty("user.timezone", "");
    TimeZone.setDefault(null);
    System.out.println(TimeZone.getDefault());
}

这是输出:

sun.util.calendar.ZoneInfo [id =“Asia/Taipei”，offset = 28800000，dstSavings = 0，useDaylight = false，transitions = 42，lastRule = null]
sun.util.calendar.ZoneInfo [id =“Asia/Hovd”，offset = 25200000，dstSavings = 0，useDaylight = false，transitions = 52，lastRule = null]
sun.util.calendar.ZoneInfo [id =“Asia/Hovd”，offset = 25200000，dstSavings = 0，useDaylight = false，transitions = 52，lastRule = null]
sun.util.calendar.ZoneInfo [id =“Asia/Hovd”，offset = 25200000，dstSavings = 0，useDaylight = false，transitions = 52，lastRule = null]
sun.util.calendar.ZoneInfo [id =“Asia/Hovd”，offset = 25200000，dstSavings = 0，useDaylight = false，transitions = 52，lastRule = null]
sun.util.calendar.ZoneInfo [id =“Europe/Kiev”，offset = 7200000，dstSavings = 3600000，useDaylight = true，transitions = 121，lastRule = java.util.SimpleTimeZone [id = Europe/Kiev，offset = 7200000， dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 2，startMonth = 2，startDay = -1，startDayOfWeek = 1，startTime = 3600000，startTimeMode = 2，endMode = 2，endMonth = 9，endDay = -1， endDayOfWeek = 1，endTime = 3600000，endTimeMode = 2]]
sun.util.calendar.ZoneInfo [id =“Europe/Kiev”，offset = 7200000，dstSavings = 3600000，useDaylight = true，transitions = 121，lastRule = java.util.SimpleTimeZone [id = Europe/Kiev，offset = 7200000， dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 2，startMonth = 2，startDay = -1，startDayOfWeek = 1，startTime = 3600000，startTimeMode = 2，endMode = 2，endMonth = 9，endDay = -1， endDayOfWeek = 1，endTime = 3600000，endTimeMode = 2]]
sun.util.calendar.ZoneInfo [id =“Europe/Kiev”，offset = 7200000，dstSavings = 3600000，useDaylight = true，transitions = 121，lastRule = java.util.SimpleTimeZone [id = Europe/Kiev，offset = 7200000， dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 2，startMonth = 2，startDay = -1，startDayOfWeek = 1，startTime = 3600000，startTimeMode = 2，endMode = 2，endMonth = 9，endDay = -1， endDayOfWeek = 1，endTime = 3600000，endTimeMode = 2]]
sun.util.calendar.ZoneInfo [id =“Europe/Kiev”，offset = 7200000，dstSavings = 3600000，useDaylight = true，transitions = 121，lastRule = java.util.SimpleTimeZone [id = Europe/Kiev，offset = 7200000， dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 2，startMonth = 2，startDay = -1，startDayOfWeek = 1，startTime = 3600000，startTimeMode = 2，endMode = 2，endMonth = 9，endDay = -1， endDayOfWeek = 1，endTime = 3600000，endTimeMode = 2]]
sun.util.calendar.ZoneInfo [id =“Europe/Kiev”，offset = 7200000，dstSavings = 3600000，useDaylight = true，transitions = 121，lastRule = java.util.SimpleTimeZone [id = Europe/Kiev，offset = 7200000， dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 2，startMonth = 2，startDay = -1，startDayOfWeek = 1，startTime = 3600000，startTimeMode = 2，endMode = 2，endMonth = 9，endDay = -1， endDayOfWeek = 1，endTime = 3600000，endTimeMode = 2]]
sun.util.calendar.ZoneInfo [id =“America/Toronto”，offset = -18000000，dstSavings = 3600000，useDaylight = true，transitions = 231，lastRule = java.util.SimpleTimeZone [id = America/Toronto，offset =- 18000000，dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 3，startMonth = 2，startDay = 8，startDayOfWeek = 1，startTime = 7200000，startTimeMode = 0，endMode = 3，endMonth = 10，endDay = 1， endDayOfWeek = 1，endTime = 7200000，endTimeMode = 0]]
sun.util.calendar.ZoneInfo [id =“America/Toronto”，offset = -18000000，dstSavings = 3600000，useDaylight = true，transitions = 231，lastRule = java.util.SimpleTimeZone [id = America/Toronto，offset =- 18000000，dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 3，startMonth = 2，startDay = 8，startDayOfWeek = 1，startTime = 7200000，startTimeMode = 0，endMode = 3，endMonth = 10，endDay = 1， endDayOfWeek = 1，endTime = 7200000，endTimeMode = 0]]
sun.util.calendar.ZoneInfo [id =“America/Toronto”，offset = -18000000，dstSavings = 3600000，useDaylight = true，transitions = 231，lastRule = java.util.SimpleTimeZone [id = America/Toronto，offset =- 18000000，dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 3，startMonth = 2，startDay = 8，startDayOfWeek = 1，startTime = 7200000，startTimeMode = 0，endMode = 3，endMonth = 10，endDay = 1， endDayOfWeek = 1，endTime = 7200000，endTimeMode = 0]]
sun.util.calendar.ZoneInfo [id =“America/Toronto”，offset = -18000000，dstSavings = 3600000，useDaylight = true，transitions = 231，lastRule = java.util.SimpleTimeZone [id = America/Toronto，offset =- 18000000，dstSavings = 3600000，useDaylight = true，startYear = 0，startMode = 3，startMonth = 2，startDay = 8，startDayOfWeek = 1，startTime = 7200000，startTimeMode = 0，endMode = 3，endMonth = 10，endDay = 1， endDayOfWeek = 1，endTime = 7200000，endTimeMode = 0]]