The differences between Java abstract classes and interfaces

• Abstract classes focus more on inheritance and derivation, whereas interfaces pay more attention to methods of contract
• Abstract classes can contain properties, and interfaces typically do not contain properties
• Abstract classes focus more on reuse, and interfaces pay more attention to the contract of the caller and the callee
• Abstract classes make it difficult for subclasses to inherit other classes, and interfaces allow classes to inherit other classes, and other interfaces can be implemented (classes are more prone to "inbreeding" errors if they implement multiple inheritance, and interfaces can scale freely horizontally)

The differences between Java abstract classes and interfaces