Please take a look at:
http://quartz.sourceforge.net/javadoc/org/quartz/Scheduler.html

In the 4th paragraph it reads:
"Job s are to be created by the 'client program', by defining a class that implements the JobDetail interface. JobDetail objects are then created (also by the client) to define a individual instances of the Job."

In the first sentence the JobDetail class is referred to as an interface. The JobDetail class should probably be replaced by the Job interface. The sentence after the first appears to have the same problem.