interface, abstract class, class one-point relationship record

An abstract class implements an interface that does not implement all the methods of the interface

Non-abstract classes implement interfaces must implement all methods.

When an abstract class implements an interface, a Non-abstract class inherits the abstract class. Both the abstract class and the Non-abstract class implement all the methods of the interface at this time.

Such as: The interface has methods 1, 2, 3

Method 1 is implemented in an abstract class. An inherited Non-abstract class implements interface methods 2, 3.