使用泛型将super（）调用到父类

Question

I have several classes that all extend the same abstract class Encoder . The abstract class requires its children to override an abstract method which accepts a generic-typed parameter ( Subscriber<T> in this example). Each subclass overriding this method uses a different type for this parameter.

abstract class Encoder<T> {

  protected String mSomeArg;

  public Encoder(String someArg) {
    mSomeArg = someArg+" super";
  }

  public abstract void start(Subscriber<T> subscriber);
}


class ExampleEncoder extends Encoder {

  public ExampleEncoder(String arg) {
    super(arg); // how to make super class get generic type?
    // eg: new Encoder<Message>(arg)
  }

  @Override
  public void start(Subscriber<Message> subscriber) {
    Message msg = new Message("hi "+mSomeArg);
    subscriber.event(msg);
  }

}

Sample use case:

Encoder sample = new ExampleEncoder();
sample.start(new Subscriber<Message>() {
  @Override
  public void event(Message msg) {
    Log(msg.text());
  }
});

Encoder otherSample = new OtherEncoder();
sample.start(new Subscriber<OtherThing>() {
  @Override
  public void event(OtherThing thing) {
    Log(thing.toString());
  }
});

Question: How can each subclass call its super() with the generic type it requires for this abstract method?

Note: Using Subscriber<?> in this abstract method for this example would defeat my purpose of using generics. Also, instantiating each subclass with the generic type it requires (eg: new ExampleEncoder<Message>() ) seems like a plausible workaround, but also seems unnecessary

Answer 1

This

class ExampleEncoder extends Encoder {

is a raw-type . I'm fairly sure you wanted something like

class ExampleEncoder extends Encoder<Message> {

if you want the concrete class to also be generic then you could use

class ExampleEncoder<T> extends Encoder<T>

but you'd need to modify start to take a Subscriber<T> .