#vulnerable code 
                                @Override
    public void putAll(Map<? extends K, ? extends V> mapToCopyIn) {
        for (Map.Entry<? extends K, ? extends V> entry : mapToCopyIn.entrySet()) {
            internalPut(entry.getKey(), entry.getValue(), false);
        }
        refreshStorage(true);
    } 
                            #location 4 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public void putAll(Map<? extends K, ? extends V> mapToCopyIn) {
        for (Map.Entry<? extends K, ? extends V> entry : mapToCopyIn.entrySet()) {
            internalPut(entry.getKey(), entry.getValue());
        }
    }