I have a base container who works with parent class.
My task – add A Child container with Child type. Just extend existing container with some specific logic for child only

But unfortunatelly it is prohibited. Example in code:

public class Test {
    public static void main() {
        Parent parent = new Parent();
        ChildContainer childContainer = new ChildContainer();
        childContainer.add(parent); // ERROR. Expected type is Child. But Parennt is given
    }

    public static class Parent { }
    public static class Child extends Parent { }

    public static class ParentContainer<T extends Parent> {
        public void add(T item) {}
        public T get() {return null;}
    }
    public static class ChildContainer extends ParentContainer<Child> { }
}

But this works with some warnings:

Parent parent = new Parent();
ParentContainer childContainer = new ChildContainer();
childContainer.add(parent);

The question is how cann use this line ot make me abble to add parennt items:

childContainer.add(parent); // ERROR. Expected type is Child.