Interfaces and abstract classes--personal learning

In Java, there is no systematic summary of many similar concepts of interfaces and abstract classes, here is a brief summary:

Interface abstract class

(1) All methods are implicitly abstract and can contain both abstract and non-abstract methods

(2) class enables multiple interfaces to inherit only one abstract class

(3) If the interface is implemented, all methods of the interface must be implemented without an abstract method

(4) All variables are final by default and can contain non-final variables

(5) The member function defaults to public, protected, private

(6) is absolutely abstract, can not be instantiated or instantiated, but if it contains the main method can be called

Interfaces and abstract classes--personal learning