In this Java 101 tutorial, I’ve explained how interfaces differ from classes, and showed you how to declare, implement, and extend interfaces in your Java programs.

Java’s standard class library contains several empty interfaces that declare no constants or method signatures. Java uses empty interfaces to tag, that is, mark object classes that are to be ...

An interface is implicitly abstract. You do not need to use the abstract keyword when declaring an interface. Each method in an interface is also implicitly abstract, so the abstract keyword is not ...