How to deal with the time encountered in the project

1. Time acquisition

/**
	 * 
	 * @Description:获取当前时间，格式yyyy-MM-dd HH:mm:ss
	 * @param type
	 *            （0,当前时间，1秒，2分，3小时，4天，5月，6年）
	 * @param time
	 *            （当前时间前后时间点）
	 * @return
	 * @version:v1
	 * @date:2017年10月24日 下午3:14:18
	 */
	public static String getStringDate(String type, int time) {
		SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		Date date = new Date();
		Calendar c = new GregorianCalendar();
		c.setTime(date);
		if ("1".equals(type)) {
			c.add(Calendar.SECOND, time);
		} else if ("2".equals(type)) {
			c.add(Calendar.MINUTE, time);
		} else if ("3".equals(type)) {
			c.add(Calendar.HOUR, time);
		} else if ("4".equals(type)) {
			c.add(Calendar.DATE, time);
		} else if ("5".equals(type)) {
			c.add(Calendar.MONTH, time);
		} else if ("6".equals(type)) {
			c.add(Calendar.YEAR, time);
		}
		date = c.getTime();
		String dateString = df.format(date);
		return dateString;
	}

2. Determine whether to run the year

public static boolean isLeapYear(String ddate) {
 
		/**
		 * 详细设计： 1.被400整除是闰年，否则： 2.不能被4整除则不是闰年 3.能被4整除同时不能被100整除则是闰年
		 * 3.能被4整除同时能被100整除则不是闰年
		 */
		Date d = strToDateLong1(ddate);
		GregorianCalendar gc = (GregorianCalendar) Calendar.getInstance();
		gc.setTime(d);
		int year = gc.get(Calendar.YEAR);
		if ((year % 400) == 0)
			return true;
		else if ((year % 4) == 0) {
			if ((year % 100) == 0)
				return false;
			else
				return true;
		} else
			return false;
	}

3. Get all months in two periods

public static List<String> getMonthBetween(String minDate, String maxDate)
			throws ParseException {
		ArrayList<String> result = new ArrayList<String>();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-M");// 格式化为年月
 
		Calendar min = Calendar.getInstance();
		Calendar max = Calendar.getInstance();
 
		min.setTime(sdf.parse(minDate));
		min.set(min.get(Calendar.YEAR), min.get(Calendar.MONTH), 1);
 
		max.setTime(sdf.parse(maxDate));
		max.set(max.get(Calendar.YEAR), max.get(Calendar.MONTH), 2);
 
		Calendar curr = max;
		while (curr.after(min)) {
			result.add(sdf.format(curr.getTime()));
			curr.add(Calendar.MONTH, -1);
		}
		return result;
	}

4. Get the specified date of the previous day

public static String getSpecifiedDayBefore(String specifiedDay)
			throws ParseException {
		Calendar c = Calendar.getInstance();
		Date date = new SimpleDateFormat("yy/MM/dd").parse(specifiedDay);
		c.setTime(date);
		int day = c.get(Calendar.DATE);
		c.set(Calendar.DATE, day - 1);
 
		String dayBefore = new SimpleDateFormat("yyyy/MM/dd").format(c
				.getTime());
		return dayBefore;
	}

5. The number of days between two dates

public static int daysBetween(String smdate, String bdate)
			throws ParseException {
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		Calendar cal = Calendar.getInstance();
		cal.setTime(sdf.parse(smdate));
		long time1 = cal.getTimeInMillis();
		cal.setTime(sdf.parse(bdate));
		long time2 = cal.getTimeInMillis();
		long between_days = (time2 - time1) / (1000 * 3600 * 24);
 
		return Integer.parseInt(String.valueOf(between_days));
	}