Programmatically determine what JDK/JRE's are installed on my box

Question

Is there a standard way to do this? I realize this can be somewhat platform dependent. Our product right now is only supported on Windows - so I suppose that's what I'm interested in right now. The only things I can think of are to either scan the registry or crawl the file system. Scanning the file system seems like it can take a really long time - and the registry can be unreliable. Should I do both? Any other suggestions? I tried to look for an API to do this with no luck.

Answer 1

System.out.println(System.getProperty("java.version"));

Other properties here

Answer 2

I would firstly start by looking for the JAVA_HOME environment variable (and possibly JDK_HOME although thats far less common) and then determining what version that is and whether it's a JDK or JRE.

After that check for common instead locations. Find out the system's program files directory (don't just assume it's C:\Program Files even though it is 99.5% of the time) and look for common install locations under that (eg Java).

I wouldn't do an exhaustive search.

It's worth asking: do you really need to find JDKs this way? Can't you just ask the user what JDK he or she wishes to use, possibly suggesting any easy ones you've found already?