在单个Java文件中使用两个Java类的性能问题

Question

I just wanted to know that is there any performance issue in

1)Using two classes in single java file.

2)Using inner java class.

I want to use it for internal data structure and supporting class. Also please tell me which one will be better in terms of performance?

Answer 1

The fact that the classes source code is in a single Java file or in two separate Java files doesn't have any impact on the byte-code: both lead to exactly the same byte-code.

An inner class is not different from any other class, except it has access to fields and methods of its enclosing class. The impact on performance is, basically, inexistent.

I concur with @EricStein: don't worry about performance before you have a real performance problem. Strive for readability, maintainability and understandability. The standard is to have one top-level class per source file. You should respect this standard.

Answer 2

Don't worry about performance until somebody notices a real problem in a production environment. Anything else is premature optimization.

That being said, don't use two top-level classes in a single java file. It's a bad code smell.

Answer 3

There is no difference between creating two classes in same file and creating inner class.

So no difference at runtime .

Answer 4

First thing,

I slightly disagree If You are comparing inner class and writing two classes in a single file .

Inner class is bounded to the Outer class as your design specification.

And writing two classes in same file is up to you(considering as a personal taste).Obviously vague and welcoming maintenance issues .

There is no matter of performance issue,Since once you compile that file a separate .class generates for each class.