Extend AND implement in the same class

Question

How can I implement an interface AND extend a class to the same class?

This doesn't seem to work (the interface is not implemented at all):

public class StrongChecker extends BasicChecker implements Checker {

This doesn't work either (the interface is not implemented at all):

public class StrongChecker extends BasicChecker {

And this gives me an error:

public class StrongChecker implements Checker extends BasicChecker {

Thanks for your help !

Answer 1

There is nothing wrong with:

public class StrongChecker extends BasicChecker implements Checker {

Of course, your StrongChecker class has to implement all the methods of Checker (or inherit implementations from BasicChecker), or the code won't compile.

Answer 2

There is nothing wrong with this syntax:

public class StrongChecker extends BasicChecker implements Checker {

This is perfectly fine just make sure you actually implement all the methods that need implementation in your interface or you will get an error.