java 获得指定日期的前一天代码收藏

/**
	 * 获得指定日期的前一天
	 * 
	 * @param specifiedDay flag flag 判断是前一天还是后一天
	 * @return
	 * @throws Exception
	 */
	public static String getSpecifiedDayBefore(String specifiedDay, String flag) {
		Calendar c = Calendar.getInstance();
		Date date = null;
		try {
			date = new SimpleDateFormat("yy-MM-dd").parse(specifiedDay);
		} catch (ParseException e) {
			e.printStackTrace();
		}
		c.setTime(date);
		int day = c.get(Calendar.DATE);
		if ("前一天".equals(flag)) {
			c.set(Calendar.DATE, day - 1);
		} else if ("后一天".equals(flag)) {
			c.set(Calendar.DATE, day + 1);
		}

		String dayBefore = new SimpleDateFormat("yyyy-MM-dd").format(c
				.getTime());
		return dayBefore;
	}