A few notes here:
* Windchill 10.2 /requires /Java 7 -- both on the server and on any
clients (e.g. applets).
o It will not run with Java 6 /at all/. The class files use the
Java 7 class file format, which Java 6 will not accept.
o The Java compiler insists on either outputting the Java 7 class
file format or disallowing use of all Java 7 language features
in the source code.
o Windchill 10.2 also uses Java APIs introduced in Java 7, so even
if the class file format was not an issue 10.2 would still
require Java 7.
* As Ben notes, one can install any number of JDKs on one machine and
have different applications using different JDKs.