Java up-transition method call issues

Base B = new Sub ();
When a Java base class variable receives a reference to a subclass object, it is transformed upward:

At this time

1, variable B can be accessed by default method is still the base class itself unique public and protected method, private method is not directly accessible to the outside world, this is always the same
"equivalent to base B = new Base ()"

2. The Sub itself is unique and does not have a method in base (whether it is public,protected or private), variable B can not access

3, but if the sub has a public or protected method that overrides the base, then variable B accesses the public and protected methods that are covered by the sub
"Private methods can never be overwritten, and cannot be accessed directly by the outside world."

Java up-transition method call issues