org.apache.commons.lang.time.DateUtils(常用的一些函数）

static java.util.Date addDays(java.util.Date date,int amount)
//Adds a number of days to a date returning a new object.
//一个日期对象＋n天
static java.util.Date addHours(java.util.Date date,int amount)
　　      //Adds a number of hours to a date returning a new object.
//一个日期对象＋n小时
static java.util.Date addMilliseconds(java.util.Date date,int amount)
//Adds a number of milliseconds to a date returning a new object.
//一个日期对象+n毫秒
static java.util.Date addMinutes(java.util.Date date,int amount)
//Adds a number of minutes to a date returning a new object.
//一个日期对象+n分
static java.util.Date addMonths(java.util.Date date,int amount)
//Adds a number of months to a date returning a new object.
//一个日期对象＋n月
static java.util.Date addSeconds(java.util.Date date,int amount)
　　      //Adds a number of seconds to a date returning a new object.
　　      //一个日期对象＋n秒
static java.util.Date addWeeks(java.util.Date date,int amount)
//Adds a number of weeks to a date returning a new object.
//一个日期对象＋N个星期
static java.util.Date addYears(java.util.Date date,int amount)
//Adds a number of years to a date returning a new object.
//一个日期对象＋N年
static boolean isSameDay(java.util.Date date1,java.util.Date date2)
//Checks if two date objects are on the same day ignoring time.
//两个日期对象是否相等（只比较年－月－日）
static boolean isSameInstant(java.util.Date date1,java.util.Date date2)
//Checks if two date objects represent the same instant in time.
//比较两个日期是否完全相等（精确到毫秒）
static java.util.Date parseDate(java.lang.String str,java.lang.String[] parsePatterns)
//Parses a string representing a date by trying a variety of different parsers.
//例 ：
String[] format={"yyyy-MM-dd"};
System.out.println(DateUtils.parseDate("2009-10-20",format));