Hi
Packet PC/SmartPhone may or may not have Java/JVM installed, its depend on handset vender. Like, as far I know i-mate have built in Java support pre-installed OS Windows Mobile 3 update. But its earlier version doesn't have installed in it!.
If java is not installed you can search for MIDlet Manager! IBM and some others have developed it, but I was not able to successfully run any java app with those.
Cheers,
Rohan Chandane