javastaticnested-class

Can a Static Nested Class be Instantiated Multiple Times?

Given what I know of every other type of static feature of programming––I would think the answer is 'no'. However, seeing statements like OuterClass.StaticNestedClass nestedObject = new OuterClass.StaticNestedClass(); makes me wonder.

Solution

  • Yes, there is nothing in the semantics of a static nested type that would stop you from doing that. This snippet runs fine.

    public class MultipleNested {
    static class Nested {
    }
    public static void main(String[] args) {
        for (int i = 0; i < 100; i++) {
            new Nested();
        }
    }
}

    See also

    Now, of course the nested type can do its own instance control (e.g. private constructors, singleton pattern, etc) but that has nothing to do with the fact that it's a nested type. Also, if the nested type is a static enum, of course you can't instantiate it at all.

    But in general, yes, a static nested type can be instantiated multiple times.

    Note that technically, a static nested type is not an "inner" type.

    JLS 8.1.3 Inner Classes and Enclosing Instances

    An inner class is a nested class that is not explicitly or implicitly declared static.

    That is, according to JLS terminology, an inner class is one that isn't static. If it's static, then it's just a nested type.

    So what does static mean?

    static simply means that the nested type does not need an instance of the enclosing type to be instantiated.

    See also