Why would a static nested interface be used in Java?

by

The static keyword in the above example is redundant (a nested interface is automatically “static”) and can be removed with no effect on semantics; I would recommend it be removed. The same goes for “public” on interface methods and “public final” on interface fields – the modifiers are redundant and just add clutter to the source code.

Either way, the developer is simply declaring an interface named Foo.Bar. There is no further association with the enclosing class, except that code which cannot access Foo will not be able to access Foo.Bar either. (From source code – bytecode or reflection can access Foo.Bar even if Foo is package-private!)

It is acceptable style to create a nested interface this way if you expect it to be used only from the outer class, so that you do not create a new top-level name. For example:

public class Foo {
    public interface Bar {
        void callback();
    }
    public static void registerCallback(Bar bar) {...}
}
// ...elsewhere...
Foo.registerCallback(new Foo.Bar() {
    public void callback() {...}
});

More Related Contents:

  1. Why can’t I declare static methods in an interface?
  2. Why are all fields in an interface implicitly static and final?
  3. Why are static variables considered evil?
  4. Calling Non-Static Method In Static Method In Java [duplicate]
  5. Java synchronized static methods: lock on object or class
  6. Why java classes do not inherit annotations from implemented interfaces?
  7. How should I have explained the difference between an Interface and an Abstract class?
  8. Can I override and overload static methods in Java?
  9. How do Java Interfaces simulate multiple inheritance?
  10. Java Interfaces Methodology: Should every class implement an interface?
  11. How to make a Java class that implements one interface with two generic types?
  12. Can we create an object of an interface?
  13. Inner class within Interface
  14. What is the “default” implementation of method defined in an Interface?
  15. Java: Static Class?
  16. How one interface can be used for different background android tasks?
  17. Should methods in a Java interface be declared with or without a public access modifier?
  18. When NOT to use the static keyword in Java?
  19. Java Reflection: Create an implementing class
  20. Closest Ruby representation of a ‘private static final’ and ‘public static final’ class variable in Java?
  21. Abstract Method Error
  22. Casting a class to an unrelated interface
  23. Final arguments in interface methods – what’s the point?
  24. What is a static interface in java?
  25. Lifetime of a static variable in Android
  26. Lambda implementation of interface in kotlin
  27. How much interfaces a class file can implement [closed]
  28. what is the actual use of interface in java? [duplicate]
  29. This appears to create an object from an interface; how does it work?
  30. What is “static”?

Leave a Comment