#vulnerable code 
                                @Override
    public int size() {
        int repoSize = nest.smembers().size();
        if (repoSize != elements.size()) {
            refreshStorage(true);
        }
        return repoSize;
    } 
                            #location 3 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public int size() {
        int repoSize = nest.smembers().size();
        return repoSize;
    }