Some really basic questions about crontab:
Can I run a java program from crontab?
If yes, how would the command line look like if I wonted to run the program every 5 minutes?
Thanks! 
You should really read the Man page for crontab.
At the command line type " man crontab". It will tell you everything you need to know.
you can run the java file using -
java -classpath path_to_class_file your_class_file_name
Remember, you have to use the full path name for 'java'. Dont forget to include all the class files in -'classpath' option.
Crontab entry -
5,10,15,20,25,30,35,40,45,50,55 * * * * your_script
Hope this is useful.
Thank you!