java - Can an interface nested inside a class be non-static?

Question

I'm reading about some articles[1][2] online about nested interface in Java, I understand that

interface A {
    ...
    interface B { // this is static by default
        ...
    }
}

But I'm not sure that

class C {
    ...
    interface D { // Is this static by default? Why?
        ...
    }
}

In short, is that "a nested interface is always static" true?

[1] https://beginnersbook.com/2016/03/nested-or-inner-interfaces-in-java/
[2] https://www.programcreek.com/2013/08/inner-interface-in-java/

Answer 1

Yes, your "in short" is always true. Quoting directly from the language spec:

A member interface is implicitly?static(§9.1.1). It is permitted for the declaration of a member interface to redundantly specify the?static?modifier.

where "member interface" is defined shortly before:

A?member interface?is an interface whose declaration is directly enclosed in the body of another class or interface declaration (§8.1.6,?§9.1.4).