private static void printUsage(String errorMessage) {
    System.err.println("ERROR: " + errorMessage);
    System.err.println(
      "Usage: hbase rowcounter [options] <tablename> " + "[--starttime=<start> --endtime=<end>] "
        + "[--range=[startKey],[endKey][;[startKey],[endKey]...]] [<column1> <column2>...]");
    System.err.println("For performance consider the following options:\n"
      + "-Dhbase.client.scanner.caching=100\n" + "-Dmapreduce.map.speculative=false");
  }
Prints usage without error message. Note that we don't document --expected-count, because it's
intended for test.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/RowCounter.java