'TheJVM'

From Jmri

Do I have Java? What version is needed?

Most systems already have a suitable Java Virtual Machine (JVM) installed. In general, if you're planning to run on a pretty modern machine, a good start would be to ensure that you have the latest version [1.5] installed. However, any version from 1.1 onwards should work and earlier versions, being smaller, tend to load faster than the behemoth that is version 1.5 :-)

[As an example, on a Pentium 166 with 128mb ram, startup time for DecoderPro went from over 30seconds before the logo appeared to less than 10 when comparing Java 1.5 to 1.3. Of course, ymmv and a discussion on this topic is hopefully taking place on the 'discussion' page above!]

Determining which Java is installed

• Windows98: Go to 'run' -> 'Command' and enter 'cmd' at the prompt. This will open a new window with a prompt something like: 'C:>'. Enter (no quotes) "java -version" and it should return the version number of your installation. If some kind of error message comes back you're going to need to download Java from Sun.
• Other Windows - Help!
• Apple Macintosh: Start a terminal window (Apps -> utilities -> terminal) and enter (still without quotes!) "java -version"
• Linux - If you're running Linux you know how to do this! :-)

Do I need the Java development kit? (The 'Java SDK')?

No, just the virtual machine!