Can a Static Nested Class be Instantiated Multiple Times?

java, nested-class, static

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

- `public static interface Map.Entry<K,V>`

- `public static class AbstractMap.SimpleEntry<K,V>`

- Probably the most well-known nested type. Obviously instantiated multiple times.

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

- Java inner class and static nested class

- Java: Static vs non static inner class

Problem

Original source

Related problems

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