Interface and abstract class

From the perspective of design

Abstract classes provide one IS-A Relationship , Then you have to satisfy the inside substitution principle , That is, the subclass object must be able to replace all the superclass objects . An interface is more like a LIKE-A Relationship , It just provides a way to implement the contract , Interfaces and classes that implement them are not required to have IS-A Relationship .

In terms of usage

A class can implement multiple interfaces , But cannot inherit multiple abstract classes .

The fields of the interface can only be static and final Type of , The fields of the abstract class have no such restriction .

The members of the interface can only be public Of , Members of abstract classes can have multiple access rights .