java 如何求出生多少天 java计算日期 多少天后

public class DateTest {

	public static void main(String[] args) {
		Date date = new Date(); // 新建一个日期

		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); // 格式化日期

		String beforeDate = sdf.format(getDateBefore(date, 10));
		System.out.println(beforeDate);
		String afterDate = sdf.format(getDateAfter(date, 10));
		System.out.println(afterDate);
	}

	/**
	 * 得到几天前的时间
	 */

	public static Date getDateBefore(Date d, int day) {
		Calendar now = Calendar.getInstance();
		now.setTime(d);
		now.set(Calendar.DATE, now.get(Calendar.DATE) - day);
		return now.getTime();
	}

	/**
	 * 得到几天后的时间
	 */

	public static Date getDateAfter(Date d, int day) {
		Calendar now = Calendar.getInstance();
		now.setTime(d);
		now.set(Calendar.DATE, now.get(Calendar.DATE) + day);
		return now.getTime();
	}
}