Using crimson after modifying it

[Alfonso Sánchez-Paus Díaz <sa...@hotmail.com>]

Hello,
I have modified the crimson org.apache.crimson.parser.inputEntity.class because it hangs the execution when you attempt to parse a document less than 8K long.
Now I am trying to use this new crimson.jar that I build so that I can overcome the problems that I got with the other.
I am trying to execute my program using: 
$ java -Xbootclasspath: "/lib/crimson-1.1.3/build/crimson.jar;/lib/j2sdk1.4/lib/tools.jar;/lib/j2sdk1.4/jre/lib/rt.jar" alfagui_1/ALFA
And I get this error message:
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object

How do I tell the jre to use the new org tree in crimson.jar instead of the one in rt.jar?
Since I only changed the InputEntity class , is there a way to make a shortcut or substitute this class from rt.jar without having to rebuild it??
Thanks a lot,
PD I know that this is not a java mailing list but I havent been able to fnd a good answer in the forums at java.sun and I guessed that maybe here you are more used to this kind of thing.