mappings.add(name_mapping);
offers.add(offer);
  public void addMapperInfo(String provider_class_name, String mime_type,                           String name_mapping)          throws IllegalArgumentException, DMDNoSuchProviderException  {    if (provider_class_name == null || provider_class_name.length() == 0        || mime_type == null || mime_type.length() == 0        || name_mapping == null || name_mapping.length() == 0)    {      throw new IllegalArgumentException();    }    if (!providers_.containsKey(provider_class_name))    {      throw new DMDNoSuchProviderException();    }    Set mappings = (Set) name_mappings_by_mime_.get(mime_type);    if (mappings == null)    {      mappings = new HashSet();      name_mappings_by_mime_.put(mime_type, mappings);    }    mappings.add(name_mapping);  }