概述
<code>TimeZone</code> represents a time zone offset, and also figures out daylight savings.
Typically, you get a <code>TimeZone</code> using <code>getDefault</code> which creates a <code>TimeZone</code> based on the time zone where the program is running.
For example, for a program running in Japan, <code>getDefault</code> creates a <code>TimeZone</code> object based on Japanese Standard Time.
TimeZone代表一个 时间区域偏移；
通常使用getDefault可以获得一个TimeZone（根据程序运行时的时区）；
比如，在日本运行的程序，会获取基于日本标准时间的TimeZone；
TimeZone timeZone = TimeZone.getDefault();
String timeZoneID = timeZone.getID();
System.out.println(timeZoneID); // Asia/Shanghai
String displayName = timeZone.getDisplayName();
System.out.println(displayName); // 中国标准时间
You can also get a <code>TimeZone</code> using <code>getTimeZone</code> along with a time zone ID.
For instance, the time zone ID for the U.S. Pacific Time zone is "America/Los_Angeles".
So, you can get a U.S. Pacific Time <code>TimeZone</code> object with:TimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
可以通过 getTimeZone获取指定的TimeZone；
比如，America/Los_Angeles将会获取 美国/洛杉矶 的TimeZone；
You can use the <code>getAvailableIDs</code> method to iterate through all the supported time zone IDs.
You can then choose a supported ID to get a TimeZone.
If the time zone you want is not represented by one of the supported IDs, then a custom time zone ID can be specified to produce a TimeZone.
可以使用getAvailableIDs查看支持的time zone IDs；
如果没有支持的，可以自定义时区ID；
The syntax of a custom time zone ID is:
自定义时区ID语法：
...
abstract public class TimeZone implements Serializable, Cloneable {
private static volatile TimeZone defaultTimeZone;
private String ID;
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;
}
private static synchronized TimeZone setDefaultZone() {
TimeZone tz;
// get the time zone ID from the system properties
String 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>() {
@Override
public Void run() {
System.setProperty("user.timezone", id);
return null;
}
});
defaultTimeZone = tz;
return tz;
}
public static TimeZone getDefault() {
return (TimeZone) getDefaultRef().clone();
}
public String getID()
{
return ID;
}
public static synchronized String[] getAvailableIDs() {
return ZoneInfo.getAvailableIDs();
}
}