Q:

Is Java runtime pre-installed on MAC OSX?

I need to port a java desktop app for mac os-x. 
The app will be launched via JNLP. 
Is the Java runtime environment pre-installed on MAC-OSX ?

A:

In general.  Java 5 or Java 6 was preinstalled on Mac OS X up to 10.6, but this ceased in 10.7.
Besides, a recent Mac OSX update uninstalls the version of Java 6 plugin previously supported by Apple.  Apple have never supported Java 7.
https://blogs.oracle.com/thejavatutorials/entry/apple_s_java_mac_os
You (or your users) need to download and install Java 7 for the Mac from Oracle.  But @Andrew Thompson's comment (see above) offers a good way to smooth that "speed bump".

