简化Java日期操作的开源项目DATE4J，超级好用 .

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以往要使用Java对时间日期进行操作，可能会用到以下的一些类：

Date and its subclasses :

java.util.Date
java.sql.Date
java.sql.Timestamp

The calendar and time zone classes :

java.util.Calendar
java.util.GregorianCalendar
java.util.TimeZone
java.util.SimpleTimeZone (for use with the Gregorian calendar only)

The formatting and parsing classes :

java.text.DateFormat
java.text.SimpleDateFormat
java.text.DateFormatSymbols

以上这么多类用起来是不是很麻烦呢，现在好了，有了DATE4J，就不用这么麻烦了。

下面是一些简单的实例：

//Examples   //Here are some quick examples of using date4j's DateTime class :   DateTime dateAndTime = new DateTime("2010-01-19 23:59:59");  DateTime dateAndTime = new DateTime("2010-01-19 23:59:59.123456789");  DateTime dateOnly = new DateTime("2010-01-19");  DateTime timeOnly = new DateTime("23:59:59");  DateTime dateOnly = DateTime.forDateOnly(2010,01,19);  DateTime timeOnly = DateTime.forTimeOnly(23,59,59,0);  DateTime dt = new DateTime("2010-01-15 13:59:15");  boolean leap = dt.isLeapYear(); //false   dt.getNumDaysInMonth(); //31   dt.getStartOfMonth(); //2010-01-01, 00:00:00.000000000   dt.getEndOfDay(); //2010-01-15, 23:59:59.999999999   dt.format("YYYY-MM-DD"); //formats as '2010-01-15'   dt.plusDays(30); //30 days after Jan 15   dt.numDaysFrom(someDate); //returns an int   dueDate.lt(someDate); //less-than   dueDate.lteq(someDate); //less-than-or-equal-to   //Although DateTime carries no TimeZone information internally, there are methods that take a TimeZone as a parameter :   DateTime now = DateTime.now(someTimeZone);  DateTime today = DateTime.today(someTimeZone);  DateTime fromMilliseconds = DateTime.forInstant(31313121L, someTimeZone);  birthday.isInFuture(someTimeZone);  dt.changeTimeZone(fromOneTimeZone, toAnotherTimeZone);

获取DATE4J.jar请访问DATE4J项目网站：http://www.date4j.net