JDK源码中对当前时间的一些用法

JDK源码中对当前时间的一些用法:

		 String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000);
		 // if no ids were returned, something is wrong. get out.
		 if (ids.length == 0)
		     System.exit(0);

		  // begin output
		 System.out.println("Current Time");

		 // create a Pacific Standard Time time zone
		 SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);

		 // set up rules for daylight savings time
		 pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
		 pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);

		 // create a GregorianCalendar with the Pacific Daylight time zone
		 // and the current date and time
		 Calendar calendar = new GregorianCalendar(pdt);
		 Date trialTime = new Date();
		 calendar.setTime(trialTime);

		 // print out a bunch of interesting things
		 System.out.println("ERA: " + calendar.get(Calendar.ERA));
		 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
		 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
		 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
		 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
		 System.out.println("DATE: " + calendar.get(Calendar.DATE));
		 System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
		 System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
		 System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
		 System.out.println("DAY_OF_WEEK_IN_MONTH: "
		                    + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
		 System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
		 System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
		 System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
		 System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
		 System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
		 System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
		 System.out.println("ZONE_OFFSET: "
		                    + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
		 System.out.println("DST_OFFSET: "
		                    + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000)));

		 System.out.println("Current Time, with hour reset to 3");
		 calendar.clear(Calendar.HOUR_OF_DAY); // so doesn't override
		 calendar.set(Calendar.HOUR, 3);
		 System.out.println("ERA: " + calendar.get(Calendar.ERA));
		 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
		 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
		 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
		 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
		 System.out.println("DATE: " + calendar.get(Calendar.DATE));
		 System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
		 System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
		 System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
		 System.out.println("DAY_OF_WEEK_IN_MONTH: "
		                    + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
		 System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
		 System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
		 System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
		 System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
		 System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
		 System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
		 System.out.println("ZONE_OFFSET: "
		        + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000))); // in hours
		 System.out.println("DST_OFFSET: "
		        + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000))); // in hours		

输出:

Current Time
ERA: 1
YEAR: 2011
MONTH: 8
WEEK_OF_YEAR: 37
WEEK_OF_MONTH: 2
DATE: 4
DAY_OF_MONTH: 4
DAY_OF_YEAR: 247
DAY_OF_WEEK: 1
DAY_OF_WEEK_IN_MONTH: 1
AM_PM: 1
HOUR: 11
HOUR_OF_DAY: 23
MINUTE: 44
SECOND: 41
MILLISECOND: 81
ZONE_OFFSET: -8
DST_OFFSET: 1
Current Time, with hour reset to 3
ERA: 1
YEAR: 2011
MONTH: 8
WEEK_OF_YEAR: 37
WEEK_OF_MONTH: 2
DATE: 4
DAY_OF_MONTH: 4
DAY_OF_YEAR: 247
DAY_OF_WEEK: 1
DAY_OF_WEEK_IN_MONTH: 1
AM_PM: 1
HOUR: 3
HOUR_OF_DAY: 15
MINUTE: 44
SECOND: 41
MILLISECOND: 81
ZONE_OFFSET: -8
DST_OFFSET: 1