public class ThreadDemo {
    private static Logger logger = Logger.getLogger(ThreadDemo.class.toString());

    static {
        new Thread(new Runnable() {
            public void run() {

                while (true) {
                    try {
                        Thread.sleep(100L);
                    } catch (InterruptedException e) {
                        logger.fine("Interrupted : " + e.getMessage());
                    }
                    logger.info("job");
                }
            }
        }).start();
    }

    public static void main(String[] args) {
        logger.info("start");
    }
}

Thread start in Static Initialization Blocks

Java