Changing jdk order

[LCID Fire]

On my Ubuntu system I have both the openjdk and sunjdk installed.
Trying to generate jni header files in ant screws up totally when 
openjdk is installed (see 
http://bugs.launchpad.net/ubuntu/+source/openjdk-6/+bug/361578). Problem 
is to compile the java stuff I need some classes that come with openjdk. 
Currently it seems like the system uses openjdk before sunjdk - is there 
a way to switch/change the orders of the jdks?