Can a Static Nested Class be Instantiated Multiple Times?

Question

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 ne

Answer 1

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

• public static interface Map.Entry
  • public static class AbstractMap.SimpleEntry
    • Probably the most well-known nested type. Obviously instantiated multiple times.

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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.

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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

• Java inner class and static nested class
• Java: Static vs non static inner class