public int reduceKeysToInt(long parallelismThreshold,
                               ToIntFunction<? super K> transformer,
                               int basis,
                               IntBinaryOperator reducer) {
        if (transformer == null || reducer == null)
            throw new NullPointerException();
        return new MapReduceKeysToIntTask<K,V>
            (null, batchFor(parallelismThreshold), 0, 0, table,
             null, transformer, basis, reducer).invoke();
    }
public int reduceKeysToInt(long parallelismThreshold,
                               ToIntFunction<? super K> transformer,
                               int basis,
                               IntBinaryOperator reducer)