Can we define inner class in interface?

Can we define inner class in interface?

Yes, you can define a class inside an interface. In general, if the methods of the interface use this class and if we are not using it anywhere else we will declare a class within an interface.

How do you declare a class inside an interface in Java?

Yes, you can create both a nested class or an inner class inside a Java interface (note that contrarily to popular belief there’s no such thing as an “static inner class”: this simply makes no sense, there’s nothing “inner” and no “outter” class when a nested class is static, so it cannot be “static inner”).

How do you declare an interface class I?

To declare a class that implements an interface, you include an implements clause in the class declaration. Your class can implement more than one interface, so the implements keyword is followed by a comma-separated list of the interfaces implemented by the class.

CAN interface have nested types?

We can declare interfaces as member of a class or another interface. Such an interface is called as member interface or nested interface. Interfaces (or classes) can have only public and default access specifiers when declared outside any other class (Refer this for details).

Can a class in an interface have an inner class?

Using your narrowed definition, interfaces can not have inner classes. You can omit the static modifier of an interface’s nested class but still, it’s a nested class, not an inner class. This answer is wrong. Interfaces can have static nested classes but not inner classes.

Can a class be declared in an interface in Java?

Interfaces may contain member type declarations (§8.5). A member type declaration in an interface is implicitly static and public. It is permitted to redundantly specify either or both of these modifiers. It is NOT possible to declare non-static classes inside a Java interface, which makes sense to me. Thank you.

How to declare an inner class in Java?

You can declare an inner class within the body of a method. These classes are known as local classes. You can also declare an inner class within the body of a method without naming the class. These classes are known as anonymous classes. You can use the same modifiers for inner classes that you use for other members of the outer class.

Where does the declaration of an inner interface occur?

Inner Interfaces. By definition, declaration of an inner interface occurs in the body of another interface or class. They are implicitly public and static as well as their fields when declared in another interface ( similar to field declarations in top-level interfaces), and they can be implemented anywhere: