Question

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，但即使更改了系统时区，java程序也会继续使用“旧”时区运行。

我怀疑Java VM在运行java程序时将默认设置为时区（Timezone.setDefault()的javadoc表示“将默认值重置为VM首次启动时的默认值。”） />

这是真的吗？ Java无法将默认时区更新为新的系统时区，因此需要重新启动VM？

Answer 1

为什么不将时区设置为声明的变量？将其初始化为默认时区，然后如果用户更改它，则将其保存到变量中。在日志中调用变量。

Answer 2

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

以下是输出：

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]]

Java时区在运行时更改

2 个答案: