is a nested class a singleton in java

Question

In Java a nested class is an inner class that is declared static. E.g.:

class Basic{

   public static class NestedClass{};
}

I am wondering if a nested class is a singleton by default, or if I may create a list of instances such as

class Basic{

   public static NestedClass{};

   List<NestedClass> items;
}

Your terminology about "nested classes" etc. is incorrect — see http://docs.oracle.com/javase/tutorial/java/javaOO/nested.html: "Nested classes are divided into two categories: static and non-static. Nested classes that are declared static are called static nested classes. Non-static nested classes are called inner classes." — Reinstate Monica -- notmaynard, Nov 26 '13 at 22:28

Óscar López · Accepted Answer · 2013-11-26T22:40:14.800

2

No, it's not a singleton (where did you get that idea?). Apart from the fact that it's a static nested class (and that does not imply that it's a singleton), it's a normal class as any other - in particular, you can create as many different instances of NestedClass as you want. If you need it to be a singleton, then you'll have to explicitly code it yourself.

edited Nov 26 '13 at 22:40

answered Nov 26 '13 at 22:17

Óscar López

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It's a static nested class. It isn't an inner class. Inner and static are mutually exclusive. – user207421 Nov 26 '13 at 22:33
You are funny asking where did I get the idea from: that's the whole point of my question: I am wondering if one implies the other. Thanks for clarifying. – Cote Mounyo Nov 26 '13 at 22:35
@CoteMounyo Everyone else is wondering the same thing. It's a perfectly good question, and you haven't answered it. Where *did* you get the idea? It doesn't make any sense. – user207421 Nov 26 '13 at 22:36

score 0 · Answer 2 · answered Nov 26 '13 at 22:32

In Java a nested class is an inner class that is declared static.

No. In Java an inner class is a nested class that is not explicitly or implicitly declared static. JLS #8.1.3. You have this back to front.

I am wondering if a nested class is a singleton by default

No.

Nesting, static, and inner have nothing to do with singletons.

is a nested class a singleton in java

2 Answers2