range

public class TestBoxImpl {

    public static EqualityComparator<T> sameObject = new EqualityComparator<T>() {
        public boolean compare(T o1, T o2) {
            return o1 == o2;
        }
    }

    public static void main(String[] args) {
        Box<Number> nBox = new BoxImpl<Number>();
        Box<Integer> iBox = new BoxImpl<Integer>();

        //sebelumnya error menjadi OK
        nBox.put(iBox);
        boolean b = nBox.containsSame(iBox, sameObject);
    }
}