public int getIndexOfKey(Object key) {
        int entry = hash[Math.abs(key.hashCode() % hashSize())];
        while (entry != 0) {
            final int idx = hash[entry];
            if (store[idx].equals(key)) { // found entry
                return idx;
            }
            entry = hash[entry + 1];
        }
        return -1;
    }
Finds the index where the key,value pair is stored.
@param key to look for
@return the index where the key is found or -1 if it is not found
vespajlib/src/main/java/com/yahoo/collections/Hashlet.java