Voici une solution qui devrait marcher. Tu sauvegardes cette classe dans le même rep que ton shell et tu lances ...
Bien sûr, tu peux donner tout le chemin absolu de ton script dans ton main java. Bonne chance.

import java.io.*;

public class ExecDemoShell {
static void lancerShell (String nomShell)
throws IOException {

// start the ls command running

Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec("ksh" + " " + nomShell);

// put a BufferedReader on the ls output

InputStream inputstream =
proc.getInputStream();
InputStreamReader inputstreamreader =
new InputStreamReader(inputstream);
BufferedReader bufferedreader =
new BufferedReader(inputstreamreader);

// read the ls output

String line;
while ((line = bufferedreader.readLine())
!= null) {
System.out.println(line);
}

// check for ls failure

try {
if (proc.waitFor() != 0) {
System.err.println("exit value = " +
proc.exitValue());
}
}
catch (InterruptedException e) {
System.err.println(e);
}
}


public static void main(String[] args)
throws IOException {
if (args.length != 1) {
System.out.println(
"missing directory");
System.exit(1);
}
lancerShell("my-script");
}
}