Please take a look at the beginner's question, thank you for answering, I will remember

plucklove

What you inherit is a class, what is the matter of the interface, it does not matter if it is implemented

kiwilose

If the class inherits the interface, all methods of the interface must be implemented. If the interface methods can be fully implemented, the abstract class can be used to inherit the interface.

glow_wy

to host:
Can you use clone as an example to write an example of compiling errors without implementing Cloneable but not being able to clone?
I studied for a long time, but didn't write it.
Unless the client program uses interface programming, and you do not implement this interface, there will be no way to compile it.