Question

let’s say i have this generic class which does some work and produces a result:

public abstract class Work<T> {

    private T mResult;

    public Work(T result) {
        mResult = result;
    }

    public abstract <T> void doWork(T result);

    public T getResult() {
        return mResult;
    }
}

For the users of this class i want type safety that would look something like this:

Work<MyResult> work = new Work<MyResult>(new MyResult()){
    public void work(MyResult result){
        //...
    }
}

The problem is Java doesn’t work this way and forces me to cast from the generic type:

Work<MyResult> work = new Work<MyResult>(new MyResult()){
    public <T> void work (T result){
        // (MyResult)result - not nice
    }
}

Is there a way to have type safety in a nice way like in the first example?

Thanks,
Teo

Answer 1

You don’t need the <T> in the declaration of doWork, because you want to use the T that is declared at the class level – you need

public abstract void doWork(T result);

The current declaration is the same as

public abstract <A> void doWork(A result);

it isn’t necessarily the same T as the rest of your class.