LearnGenerics.java

public class LearnGenerics {
    static abstract class AbsRecursive<A extends AbsRecursive<A, T>, T> {
        RecursiveListener<A, ? super T> mListener;
        T mItem;

        public <XA extends AbsRecursive<XA, ? super T>>
        void setListener(RecursiveListener<? super XA, ? super T> listener) {
            // FIXME: I could not fix this.
            @SuppressWarnings("unchecked")
            RecursiveListener<A, ? super T> l = (RecursiveListener<A, ? super T>) listener;
            mListener = l;
        }

        public void doHoge() {
            mListener.onHoge(getSelf(), mItem);
        }

        public abstract A getSelf();
    }

    static class Recursive<T> extends AbsRecursive<Recursive<T>, T> {
        @Override
        public Recursive<T> getSelf() {
            return this;
        }
    }

    static class StrRecursive extends Recursive<String> {

    }

    static class ObjRecursive extends Recursive<Object> {

    }

    static class RecursiveListener<A extends AbsRecursive<A, T>, T> {
        public void onHoge(A adapter, T object) {

        }
    }

    void doRecursive() {
        ObjRecursive objRecursive = new ObjRecursive();
        StrRecursive strRecursive = new StrRecursive();

        RecursiveListener<Recursive<Object>, Object> objListener = new RecursiveListener<>();
        RecursiveListener<Recursive<String>, ? super String> strListener = new RecursiveListener<>();

        objRecursive.setListener(objListener);
        strRecursive.setListener(strListener);
        strRecursive.setListener(objListener);
    }
}