public String checksumRows(final Table table) throws Exception {

    Scan scan = new Scan();
    ResultScanner results = table.getScanner(scan);
    MessageDigest digest = MessageDigest.getInstance("MD5");
    for (Result res : results) {
      digest.update(res.getRow());
    }
    results.close();
    return digest.toString();
  }
Return an md5 digest of the entire contents of a table.
hbase-testing-util/src/main/java/org/apache/hadoop/hbase/HBaseTestingUtility.java