public boolean containsKey(final Object key) {
        final Entry<K, V>[] tbl = mapTable;
        if (key != null) {
            final int hashCode = key.hashCode();
            final int index = (hashCode & 0x7FFFFFFF) % tbl.length;
            for (Entry<K, V> e = tbl[index]; e != null; e = e.next) {
                if (e.hashCode == hashCode && key.equals(e.key)) {
                    return true;
                }
            }