class Configuration implements Iterable<Map.Entry<String,String>>,
                                      Writable {

  public Class<?>[] getClasses(String name, Class<?> ... defaultValue) {
    String valueString = getRaw(name);
    if (null == valueString) {
      return defaultValue;
    }
    String[] classnames = getTrimmedStrings(name);
    try {
      Class<?>[] classes = new Class<?>[classnames.length];
      for(int i = 0; i < classnames.length; i++) {
        classes[i] = getClassByName(classnames[i]);
      }
      return classes;
    } catch (ClassNotFoundException e) {
      throw new RuntimeException(e);
    }
  }

  public  Configuration();
  public  Configuration(boolean loadDefaults);
  @SuppressWarnings("unchecked") public  Configuration(Configuration other);

}