possible.

 <p>
 If the value ranges implied by the two bounds are not overlapping or adjacent, then null is returned.
 Otherwise an instance is returned that corresponds to the union of the two implied value ranges.

 <p>
 Some cases not handled, e.g., when one bound has an inclusive upper bound with value <i>x</i> and the
 other has an inclusive lower bound with value <i>x + 1</i>, because this method can't detect adjacent values.</div>
<dl class="notes">
<dt>Parameters:</dt>
<dd><code>comparator</code> -