Java: How to check if an object is an instance of a non-static inner class, regardless of the outer object?

Question

If I have an inner class e.g.

class Outer{
    class Inner{}
}

Is there any way to check if an arbitrary Object is an instance of any Inner, regardless of its outer object? instanceof gives false when the objects are not Inners from the same Outer. I know a workaround is just to make Inner a static class, but I'm wondering if what I'm asking is possible.

Example:

class Outer{
    Inner inner = new Inner();
    class Inner{}

    public boolean isInner(Object o){
        return o instanceof Inner;
    }
}

Outer outer1 = new Outer();
Outer outer2 = new Outer();
boolean answer = outer1.isInner(outer2.inner); //gives false

Answer 1

And what about?

public static boolean isInnerClass(Class<?> clazz) {
    return clazz.isMemberClass() && !Modifier.isStatic(clazz.getModifiers());
}

The method isMemberClass() will test if the method is a member (and not an anonymous or local class) and the second condition will verify that your member class is not static.

By the way, the documentation explains the differences between local, anonymous and nested classes.

Nested classes are divided into two categories: static and non-static. Nested classes that are declared static are simply called static nested classes. Non-static nested classes are called inner classes.