public TypeV setValue(final TypeV val) {
      if (val == null) throw new NullPointerException();
      _val = val;
      return put(_key, val);
    }
Keys as a long array.  Array may be zero-padded if keys are concurrently deleted.
jctools-core/src/main/java/org/jctools/maps/NonBlockingHashMapLong.java