code: public SimpleJob setCombiner(Class<? extends Reducer<Key, Value, Key, Value>> clazz,
                                   int cache)
              throws IllegalStateException {
          super.setCombinerClass(clazz);
          getConfiguration().setInt(COMBINE_CACHE, cache);
          return this;
      }
docs: Job Conbiner class setting.
  @param clazz {@link Summarizer} class
  @param cache In-Mapper Combine output cahce number. Default value is 200.
  @return this