core/src/main/java/com/twitter/elephantbird/mapreduce/input/MultiInputFormat.java
private void setTypeRef(Configuration conf) {
    String className = conf.get(CLASS_CONF_KEY);

    if (className == null) {
      throw new RuntimeException(CLASS_CONF_KEY + " is not set");
    }

    Class<?> clazz = null;
    try {
      clazz = conf.getClassByName(className);
    } catch (ClassNotFoundException e) {
      throw new RuntimeException("failed to instantiate class '" + className + "'", e);
    }

    typeRef = new TypeRef<M>(clazz){};
  }
private void setTypeRef(Configuration conf) {
    String className = conf.get(CLASS_CONF_KEY);

    if (className == null) {
      throw new RuntimeException(CLASS_CONF_KEY + " is not set");
    }

    Class<?> clazz = null;
    try {
      clazz = conf.getClassByName(className);
    } catch (ClassNotFoundException e) {
      throw new RuntimeException("failed to instantiate class '" + className + "'", e);
    }

    typeRef = new TypeRef<M>(clazz){};
  }
set typeRef from conf