@Override
    public V get(byte key) {
        int index = indexOf(key);
        return index == -1 ? null : toExternal(values[index]);
    }
The load factor for the map. Used to calculate {@link #maxSize}.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/util/ByteObjectHashMap.java