finding the java path in ubuntu is easy, just follow the links... most links live in /usr/bin so:
mike@mbox:/$ ls -l /usr/bin/java
lrwxrwxrwx 1 root root 22 2008-12-07 22:16 /usr/bin/java -> /etc/alternatives/java
mike@mbox:/$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 40 2008-12-07 22:34 /etc/alternatives/java -> /usr/lib/jvm/java-6-openjdk/jre/bin/java