cron4j is a scheduler for the Java platform.
Editor: cron4j is a scheduler for the Java platform which is very Similar to the UNIX cron daemon. With cron4j you can launch, from within your Java applications, any task you need at the right time, according to some simple rules.
The Java 2 platform already has a built-in scheduler, implemented with the class java.util.Timer. The cron4j scheduler, however, acts in a different way. You can say to the java.util.Timer scheduler something like launch this task after 5 minutes from now or launch it after 5 minutes from now, then repeat it every 10 minutes. Thats all. The cron4j scheduler, instead, lets you do something a Little more complex, like launch this task every Monday, at 12:00, launch it every 5 minutes, but dont launch it during the weekend, launch it every hour Between the 8:00AM and the 8:00PM and launch it every 5 minutes between the 8:00PM and the 8:00AM, launch it once every day but Sunday, during every month but July and August and so on, and all that with a single line of code.
Programming the cron4j scheduler is easy, you have to know just a few methods. The launching rules for every task must be expressed with a String called scheduling pattern, whose syntax is equal to the one used by the UNIX crontab entries. If you know how to manipulate the UNIX crontab, the most is done. If you cant, dont worry: crontab scheduling patterns rules are very simple and you can learn them in minutes. By the way, you will find them explained in the cron4j documentation.

RELEASE 2.2.3 - 2010-05-30

- A bug has been fixed in the ProcessTask class, avoiding the too many open files problem encountered on some systems.
- A bug has been fixed in the SchedulingPattern class,avoiding the possibility to use a value greater than
23 in the hour field of a scheduling pattern. you can free download cron4j 2.2.3 now.