Question

I wanna re-run a jar file from its own (with some additional parameters). How can I do this?
I need the solution to be OS independent.

Answer 1

If I deciphered the question correctly, we are talking about command line interface arguments. For this there’s plenty tutorials: http://docs.oracle.com/javase/tutorial/essential/environment/cmdLineArgs.html

The code is simple, like you said yourself:

if ("-server".equalsIgnoreCase(argv)) {
    // we are server
} else if ("-client".equalsIgnoreCase(argv)) {
    // we are client
}

Now, depending on how you want to execute you program from the OS, there’s a number of ways:

$java -jar yourjar.jar -client

Or

$java -cp yourjar.jar com.your.program.Main -client

Same for the “-server”.

To run them together, either run them from separate terminal windows (or cmd prompts). Or – if in Linux – you can use ampersand:

$java -jar yourjar.jar -client &
$java -jar yourjar.jar -server &