Should an interface extending another interface specify overrides?

Or in particular: What is the difference between

interface A {
   void fa();
}
    
interface B extends A {
   void fa();

   void fb();
}

and

interface A {
   void fa();
}
    
interface B extends A {
   @Override
   void fa();

   void fb();
}

Does it effect the implementing class in any way?

Answer

No it should not. The class that implements interface B will still have to provide an implementation of void fa(); regardless whether interface B annotates the same method signature with @Override or not. Also, putting the @Override annotation in interface B doesn’t make a lot of sense in this case because the annotation basically means that you are overriding the implementation that the super class gave to that method signature. Since Interface A nor Interface B provides an implementation to void fa() it doesen’t make sense.

It would make sense if interface A provided a default implementation to void fa() For example:

interface A {
   public default void fa(){
     System.out.println("My default implementation");
   }
}

In this case Interface B would be overriding the implementation given to fa() from Interface A by making it abstract again. The same goes when Interface A defines fa() as abstract and Interface B gives it an implementation by turning it into a default method.