code: public static long countRows(Configuration conf, byte[] tableName) throws IOException {
          HTable hTable = null;
          ResultScanner rs = null;
          long count = 0;
          try {
              hTable = new HTable(conf, tableName);
              rs = hTable.getScanner(new Scan());
              for(@SuppressWarnings("unused") Result r: rs) {
                  count++;
              }
              return count;
          } finally {
              if(hTable != null) {
                  hTable.close();
              }
              if(rs != null) {
                  rs.close();
              }
          }
      }
docs: Only use this for testing/debugging. Inefficient.