private static byte[] checkStartKey(byte[] startKey) {
    return startKey == null ? HConstants.EMPTY_START_ROW : startKey;
  }
The new format for a region name contains its encodedName at the end. The encoded name also
serves as the directory name for the region in the filesystem. New region name format:
&lt;tablename>,,&lt;startkey>,&lt;regionIdTimestamp>.&lt;encodedName>. where, &lt;encodedName>
is a hex version of the MD5 hash of &lt;tablename>,&lt;startkey>,&lt;regionIdTimestamp> The old
region name format: &lt;tablename>,&lt;startkey>,&lt;regionIdTimestamp> For region names in the
old format, the encoded name is a 32-bit JenkinsHash integer value (in its decimal notation,
string form).
<p>
**NOTE** The first hbase:meta region, and regions created by an older version of HBase (0.20 or
prior) will continue to use the old region name format.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/MutableRegionInfo.java