How influence static nested class performance and memory

Question

I have a class i.e. Category. Its a POJO with some member variables and getters and it can be instanciated. Category contains a static nested class called Contract. The Contract contains only constants like column names of a database table. Last but not least contains the Category also a static Builder to configure a new Category and instanciate this one.

class Category {
   static class Contract{}
   static class Builder{}
}

Can their be a problem about performance or memory with this class structure? I mean by 100 Categories and each one has a Contract and a Builder. Any help or infos are welcome.

Possible duplicate of [What is the memory consumption of an object in Java?](http://stackoverflow.com/questions/258120/what-is-the-memory-consumption-of-an-object-in-java) — shmosel, Jan 06 '17 at 23:13
There is no such thing as a "static inner class" in Java. "The static keyword may modify the declaration of a member type C within the body of a non-inner class or interface T. Its effect is to declare that C is not an inner class." https://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.5.1 "An inner class is a nested class that is not explicitly or implicitly declared static." https://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.1.3 — Lew Bloch, Jan 06 '17 at 23:17
you mean 100 Category instances or 100 classes like Category? also which kind of performance or memory impact you are concerned about? any background of what this is for? — Jason Hu, Jan 06 '17 at 23:22
['Static inner' is a contradiction in terms](http://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.1.3). — user207421, Jan 07 '17 at 01:34
Sorry for the confusion about "inner" and "nested" class. I changed the title and description. — Happo, Jan 09 '17 at 05:31

score 0 · Answer 1 · answered Jan 06 '17 at 23:18

0

Whether or not you have a performance or memory issue is entirely a matter of how the classes are defined and used, and is not affected by whether they're nested classes or not.

answered Jan 06 '17 at 23:18

Lew Bloch

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score 0 · Accepted Answer · answered Jan 06 '17 at 23:48

No instance of the static nested classes will be created when you create an instance of the Category class. So no memory impact (the code will behave, from a memory perspective, as if the nested classes had been declared as top level classes).

Had they been inner classes (not static) the answer would be different.

How influence static nested class performance and memory

2 Answers2