为什么没有传入指定时区情况下new Date会正确显示当地时间
Date date = new Date();
log.info(date.toString())
默认构造方法
public Date() {this(System.currentTimeMillis());
}public Date(long date) {fastTime = date;
}System.currentTimeMillis()是jvm通过c语言实现的获取UTC时间戳的方法，看到这里还是没看到时区，继续往下看.
我们是通过toString()打印当地时间信息的，我们看代码
public String toString() {// "EEE MMM dd HH:mm:ss zzz yyyy";BaseCalendar.Date date = normalize();StringBuilder sb = new StringBuilder(28);int index = date.getDayOfWeek();if (index == BaseCalendar.SUNDAY) {index = 8;}convertToAbbr(sb, wtb[index]).append(' '); // EEEconvertToAbbr(sb, wtb[date.getMonth() - 1 + 2 + 7]).append(' '); // MMMCalendarUtils.sprintf0d(sb, date.getDayOfMonth(), 2).append(' '); // ddCalendarUtils.sprintf0d(sb, date.getHours(), 2).append(':'); // HHCalendarUtils.sprintf0d(sb, date.getMinutes(), 2).append(':'); // mmCalendarUtils.sprintf0d(sb, date.getSeconds(), 2).append(' '); // ssTimeZone zi = date.getZone();if (zi != null) {sb.append(zi.getDisplayName(date.isDaylightTime(), TimeZone.SHORT, Locale.US)); // zzz} else {sb.append("GMT");}sb.append(' ').append(date.getYear()); // yyyyreturn sb.toString();}继续看normalize方法
private final BaseCalendar.Date normalize() {if (cdate == null) {BaseCalendar cal = getCalendarSystem(fastTime);cdate = (BaseCalendar.Date) cal.getCalendarDate(fastTime,TimeZone.getDefaultRef());return cdate;}// Normalize cdate with the TimeZone in cdate first. This is// required for the compatible behavior.if (!cdate.isNormalized()) {cdate = normalize(cdate);}// If the default TimeZone has changed, then recalculate the// fields with the new TimeZone.TimeZone tz = TimeZone.getDefaultRef();if (tz != cdate.getZone()) {cdate.setZone(tz);CalendarSystem cal = getCalendarSystem(cdate);cal.getCalendarDate(fastTime, cdate);}return cdate;}TimeZone.getDefaultRef()方法返回时区，继续看
static TimeZone getDefaultRef() {TimeZone defaultZone = defaultTimeZone;if (defaultZone == null) {// Need to initialize the default time zone.defaultZone = setDefaultZone();assert defaultZone != null;}// Don't clone here.return defaultZone;}setDefaultZone方法
private static synchronized TimeZone setDefaultZone() {TimeZone tz;// get the time zone ID from the system propertiesString zoneID = AccessController.doPrivileged(new GetPropertyAction("user.timezone"));// if the time zone ID is not set (yet), perform the// platform to Java time zone ID mapping.if (zoneID == null || zoneID.isEmpty()) {String javaHome = AccessController.doPrivileged(new GetPropertyAction("java.home"));try {zoneID = getSystemTimeZoneID(javaHome);if (zoneID == null) {zoneID = GMT_ID;}} catch (NullPointerException e) {zoneID = GMT_ID;}}// Get the time zone for zoneID. But not fall back to// "GMT" here.tz = getTimeZone(zoneID, false);if (tz == null) {// If the given zone ID is unknown in Java, try to// get the GMT-offset-based time zone ID,// a.k.a. custom time zone ID (e.g., "GMT-08:00").String gmtOffsetID = getSystemGMTOffsetID();if (gmtOffsetID != null) {zoneID = gmtOffsetID;}tz = getTimeZone(zoneID, true);}assert tz != null;final String id = zoneID;AccessController.doPrivileged(new PrivilegedAction<Void>() {@Overridepublic Void run() {System.setProperty("user.timezone", id);return null;}});defaultTimeZone = tz;return tz;}最终看到通过jvm系统属性user.timezone获取当前时区，并结合时间戳，转换为当地正确的时间
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