Java.lang.Class.cast doesn't return a casted object

I am trying to cast an object to its superclass using Java.lang.Class.cast but I get the same object. What can be the reason?

This is the code I'm running:

public static void parse(Object obj)
{
    // parse all super classes
    Class<?> clazz = obj.getClass().getSuperclass();
    if (!clazz.equals(prevClass))
    {
        prevClass = clazz;
        Object castedObj = clazz.cast(obj);
        parse(castedObj);   
    }
    fillObject(obj);
}

but when passing to parse an object of dynamic type B, where B extends A, castedObj is equal to obj. But I want castedObj to be a new object of dynamic type A because the parse method relies on that fact (iterates on the fields of the dynamic type class).