* stripes, the intended concurrency level, and the typical number of keys used in a {@code
   * bulkGet(keys)} operation. See <a href="http://www.mathpages.com/home/kmath199.htm">Balls in
   * Bins model</a> for mathematical formulas that can be used to estimate the probability of
   * collisions.
   *
   * @param keys arbitrary non-null keys

   * Apache <a href="http://httpd.apache.org/">HTTPD project</a>; for the specification, see <a
   * href="http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/PhotoshopFileFormats.htm">
   * Adobe Photoshop Document Format</a> and <a
   * href="http://en.wikipedia.org/wiki/Adobe_Photoshop#File_format">Wikipedia</a>; this is the