LockTest2.java

private static Map<Integer,Object> LOCKS = new ConcurrentHashMap<>();
private static void mayLock(Integer arg)  {
    logger.info("entering method {} ", arg);
    synchronized (LOCKS.computeIfAbsent(arg,f->new Object())){
        logger.info("entering lock "+Thread.currentThread().getName());
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}