code: public Class<? extends CompressionCodec>
    getMapOutputCompressorClass(Class<? extends CompressionCodec> defaultValue) {
      Class<? extends CompressionCodec> codecClass = defaultValue;
      String name = get("mapred.map.output.compression.codec");
      if (name != null) {
        try {
          codecClass = getClassByName(name).asSubclass(CompressionCodec.class);
        } catch (ClassNotFoundException e) {
          throw new IllegalArgumentException("Compression codec " + name +
                                             " was not found.", e);
        }
      }
      return codecClass;
    }
docs: Get the {@link CompressionCodec} for compressing the map outputs.
  
  @param defaultValue the {@link CompressionCodec} to return if not set
  @return the {@link CompressionCodec} class that should be used to compress the
  map outputs.
  @throws IllegalArgumentException if the class was specified, but not found