private static Class<? extends InputFormat> getConfiguredInputFormat(Job job) {
    return (Class<? extends InputFormat>) job.getConfiguration().getClass(TABLE_INPUT_CLASS_KEY,
      TableInputFormat.class);
  }
@return {@link TableInputFormat} .class unless Configuration has something else at
        {@link #TABLE_INPUT_CLASS_KEY}.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableMapReduceUtil.java