How to allow running only one instance of a Java program at a time?

Question

I need to prevent users from starting my Java application (WebStart Swing app) multiple times. So if the application is already running it shouldn\'t be possible to start it

Answer 1

Try JUnique:

String appId = "com.example.win.run.main";
boolean alreadyRunning;
try {
    JUnique.acquireLock(appId);
    alreadyRunning = false;
} catch (AlreadyLockedException e) {
    alreadyRunning = true;
}
if (alreadyRunning) {
    Sysout("An Instance of this app is already running");
    System.exit(1);
}