How Can I Create a Single-Instance Java Application Using File Locking?

Creating Single Instance Java Applications: A Robust Approach

Single instance applications, such as MSN or Windows Media Player, prevent multiple instances of the same application from running simultaneously. For Java developers, achieving this functionality requires a different approach than using Mutex in C#.

The recommended method for creating single instance Java applications is leveraging file locking. This technique enables the application to obtain exclusive access to a designated lock file while it's running. If another instance attempts to run while the application is active, it will be blocked until the lock is released.

To implement file locking, utilize the following code snippet:

private static boolean lockInstance(final String lockFile) {
    try {
        final File file = new File(lockFile);
        final RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
        final FileLock fileLock = randomAccessFile.getChannel().tryLock();
        if (fileLock != null) {
            Runtime.getRuntime().addShutdownHook(new Thread() {
                public void run() {
                    try {
                        fileLock.release();
                        randomAccessFile.close();
                        file.delete();
                    } catch (Exception e) {
                        log.error("Unable to remove lock file: " + lockFile, e);
                    }
                }
            });
            return true;
        }
    } catch (Exception e) {
        log.error("Unable to create and/or lock file: " + lockFile, e);
    }
    return false;
}

By implementing this method, your Java application can effectively prevent multiple instances from running concurrently.

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