Java typecasting and raw types

Question

GeneratedMessage.Builder is a static nested class inside GeneratedMessage (both of them are abstract classes). When the method build() is called on an object of type GeneratedMessage.Builder, it returns an object of type GeneratedMessage. Is there some way to declare my raw types T and B in the following example, which would make the typecasting in the return statement of convert() needless.

public class JsonStringToMessageConverter<T extends GeneratedMessage, B extends GeneratedMessage.Builder<B>>
        implements IConverter<String, T> {
  private final IPbBuilderProvider<B> m_builderProvider;

  @Inject
  public JsonStringToMessageConverter(IPbBuilderProvider<B> builderProvider) {
    m_builderProvider = builderProvider;
  }

  @Override
  public final T convert(String value) {
    B builder = m_builderProvider.getPbBuilder();
    try {
      JsonFormat.merge(value, builder);
    } catch (ParseException e) {
      throw new LoggedRuntimeException(ErrorType.PARSE_FAILED, e);
    }
    return (T) builder.build();
  }
}

The class GeneratedMessage is defined in Google's Protobuf library.

Answer 1

You should use type parameter in the Builder for build() method return type and declare it as extends GeneratedMessage .

As I see the build method is not generic, so you cannot do it, I'm afraid.

Answer 2

No there is not since the build method is defined within the Message.Builder class and that class is not generic. The build method returns a Message object not some generic extension of the Message class. Therefore there is no generic manipulation of GeneratedMessage.Builder that will cause the method signature of build return anything other than Message .