How does Calendar.getInstance() know the current year?

How does Calendar.getInstance() method get you the current year? It doesn't read it from your computer obviously neit开发者_JAVA技巧her from the internet. This may sound like a newbie question but how does this method work?

Actually, it does read it from your computer. Internally, it calls GregorianCalendar's constructor, which calls System.currentTimeMillis(), which is a native method.

Depending on your locale, it might also create a JapaneseImperialCalendar or a BuddhistCalendar, which also both call System.currentTimeMillis().

Calendar.getInstance()

is just a shortcut for

new GregorianCalendar()

which initializes itself using:

setTimeInMillis(System.currentTimeMillis());

So the trick is

System.currentTimeMillis()

which indeed does read it from your computer.