What might be the difference between getting datetime using
Calendar.getIn开发者_如何转开发stance() 
vs
new GregorianCalendar()
?
Looking in the source of Calendar.getInstance():
private static Calendar createCalendar(TimeZone zone, Locale aLocale) {
    // If the specified locale is a Thai locale, returns a BuddhistCalendar
    // instance.
    if ("th".equals(aLocale.getLanguage())
        && ("TH".equals(aLocale.getCountry()))) {
        return new sun.util.BuddhistCalendar(zone, aLocale);
    } else if ("JP".equals(aLocale.getVariant())
        && "JP".equals(aLocale.getCountry())
        && "ja".equals(aLocale.getLanguage())) {
        return new JapaneseImperialCalendar(zone, aLocale);
    }       
    // else create the default calendar
    return new GregorianCalendar(zone, aLocale);    
}
So getInstance() will return a Calendar based on your default Locale and TimeZone.
Calendar.getInstance() will give you a Calendar using the default time zone and locale, which can result in a GregorianCalendar, a BuddhistCalendar, or a JapaneseImperialCalendar.
GregorianCalendar will always give you, well, a Gregorian calendar.
 
         
                                         
                                         
                                         
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