Return to Question

I initially wanted to put the concrete classes as generic types in the implementation of TransformStrategy to avoid the cast, but that does not work, because the implementation cannot be inserted into the constructor of the transformer. This problem is shortly described with this example:

abstract class AnswerConstraint { }
class LengthConstraint extends AnswerConstraint { }

interface TransformStrategy<T, S> { /* some method */ }
class LengthConstraintTransformStrategy implements TransformStrategy<LengthConstraint, LengthConstraintResource> { /* implementation */}

class Main {
    public static void main(String[] args) {

        List<TransformStrategy<AnswerConstraint, AnswerConstraintResource>> list = new ArrayList<>();

        // this fails although AnswerConstraint is the supertype of LengthConstraint and AnswerConstraintResource the supertype of LengthConstraintResource
        list.add(new LengthConstraintTransformStrategy());
    }
}

I initially wanted to put the concrete classes as generic types in the implementation of TransformStrategy to avoid the cast, but that does not work, because the implementation cannot be inserted into the constructor of the transformer. This problem is shortly described with this example (using the classes from above):

class LengthConstraintTransformStrategy implements TransformStrategy<LengthConstraint, LengthConstraintResource> { /* implementation */}

class Main {
    public static void main(String[] args) {

        List<TransformStrategy<AnswerConstraint, AnswerConstraintResource>> list = new ArrayList<>();

        // this fails although AnswerConstraint is the supertype of LengthConstraint and AnswerConstraintResource the supertype of LengthConstraintResource
        list.add(new LengthConstraintTransformStrategy());
    }
}

I initially wanted to put the concrete classes as generic types in the implementation of TransformStrategy, but that does not work, because the implementation cannot be inserted into the constructor of the transformer. This problem is shortly described with this example:

abstract class Base { }
class Concrete extends Base { }

interface Something<T> { /* some method */ }
class Implementation implements Something<Concrete> { /* implementation */}

class Main {
    public static void main(String[] args) {

        List<Something<Base>> list = new ArrayList<>();

        // this fails although Base is the supertype of Concrete
        list.add(new Implementation());
    }
}

I initially wanted to put the concrete classes as generic types in the implementation of TransformStrategy to avoid the cast, but that does not work, because the implementation cannot be inserted into the constructor of the transformer. This problem is shortly described with this example:

abstract class AnswerConstraint { }
class LengthConstraint extends AnswerConstraint { }

interface TransformStrategy<T, S> { /* some method */ }
class LengthConstraintTransformStrategy implements TransformStrategy<LengthConstraint, LengthConstraintResource> { /* implementation */}

class Main {
    public static void main(String[] args) {

        List<TransformStrategy<AnswerConstraint, AnswerConstraintResource>> list = new ArrayList<>();

        // this fails although AnswerConstraint is the supertype of LengthConstraint and AnswerConstraintResource the supertype of LengthConstraintResource
        list.add(new LengthConstraintTransformStrategy());
    }
}