Java --日期日历操作

	public static void main(String[] args) throws ParseException {
		
		//1、将指定格式字符串转换成日期
		String dateString = "2017/11/28 14:23:12";
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
		Date date = sdf.parse(dateString);
		System.out.println(date.toLocaleString());//2017-11-28 14:23:12
		//日期转指定格式字符串
		String _date = sdf.format(new Date());
		System.out.println(_date);//2017/11/28 14:42:50
		
		//2、如何取得年月日星期、小时分秒?
		Calendar cal = Calendar.getInstance();
		int year = cal.get(Calendar.YEAR);//年
		System.out.println(year);//2017
		int month = cal.get(Calendar.MONTH)+1;//月，要+1
		System.out.println(month);//11
		int day = cal.get(Calendar.DATE);//日
		System.out.println(day);//28
		int hour_12 = cal.get(Calendar.HOUR);//12小时制
		System.out.println(hour_12);//1
		int hour_24 = cal.get(Calendar.HOUR_OF_DAY);//24小时制
		System.out.println(hour_24);//13
		int minute = cal.get(Calendar.MINUTE);//分钟
		System.out.println(minute);//52
		int second = cal.get(Calendar.SECOND);//秒
		System.out.println(second);//10
		int day_month = cal.get(Calendar.DAY_OF_MONTH);//本月第几天
		System.out.println(day_month);//28
		int week = cal.get(Calendar.DAY_OF_WEEK);//星期
		System.out.println(week);//3,周日是1
		int week_month = cal.get(Calendar.WEEK_OF_MONTH);//当月第几个星期
		System.out.println(week_month);//5

		//3、如何取得从1970 年到现在的毫秒数?
		long timeInMillis = cal.getTimeInMillis();
		System.out.println(timeInMillis);//1511848647459
		long currentTimeMillis = System.currentTimeMillis();
		System.out.println(currentTimeMillis);//1511848647459
		
		//4、如何取得某个日期是当月的最后一天?
		int lastDay = cal.getActualMaximum(Calendar.DATE);
		int firstDay = cal.getActualMinimum(Calendar.DATE);
		System.out.println(lastDay+":"+firstDay);//30:1
		
		//5、将当前日期设置成某一天
		cal.set(Calendar.YEAR, 2012);
		cal.set(Calendar.MONTH, 0);
		cal.set(Calendar.DATE, 1);
		cal.set(Calendar.HOUR_OF_DAY, 1);
		cal.set(Calendar.MINUTE, 1);
		cal.set(Calendar.SECOND, 1);
		Date time = cal.getTime();
		System.out.println(time.toLocaleString());//2012-1-1 1:01:01
		
		//6、求当前天数的后一天、前一天
		cal.add(Calendar.DATE, 1);
		Date time2 = cal.getTime();
		System.out.println(time2.toLocaleString());//2012-1-2 1:01:01
		cal.add(Calendar.DATE, -1);
		Date time3 = cal.getTime();
		System.out.println(time3.toLocaleString());//2012-1-1 1:01:01

	}