#vulnerable code 
                                public void remove(User user) {
        this.users.remove(user.getRank());

        synchronized (users) {
            Collections.sort(this.users);
        }
    } 
                            #location 2 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public void remove(User user) {
        this.users.remove(user.getRank());

        Collections.sort(this.users);
    }