Java coding convention about static method

Question

It is a very simple question, but I think it is a little bit controversial.

When I code Java classes I use the following order.

class Foo {

    // static fields
    // instance fields
    // constructors
    // methods (non-static and static methods are mixed but sorted based on their functionalities)
}

I read an article that says:
(From http://code.google.com/webtoolkit/makinggwtbetter.html#codestyle)

Java types should have the following member order:

Nested Types (mixing inner and static classes is okay)
Static Fields
Static Initializers
Static Methods
Instance Fields
Instance Initializers
Constructors
Instance Methods

If I follow the article, the order above should be

class Foo {

    // static fields
    // static methods
    // instance fields
    // constructors
    // instance methods
}

In the case of the latter, I feel uncomfortable having some methods before constructors. Which one is the more widely-used convention?

score 24 · Accepted Answer · answered Sep 23 '11 at 14:31

24

I believe Sun's (now Oracle's) Java coding standards are more widely used. This is what you are currently using too.

From Code Conventions for the Java TM Programming Language :

3.1.3 Class and Interface Declarations

The following table describes the parts of a class or interface declaration, in the order that they should appear.

Class/interface documentation comment ( /*.../)

class or interface statement

Class/interface implementation comment ( /.../), if necessary

Class (static) variables

Instance variables

Constructors

Methods

answered Sep 23 '11 at 14:31

dogbane

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Hmm I see. I think I am using standards. Some of Google's coding styles make me confused, especially Android examples in sdk. – Heejin Sep 23 '11 at 14:37
4

what about static methods vs methods? – ealeon Feb 20 '19 at 16:09
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If doesn't say anything specifically about static methods though. I typically put them above instance variables if they are public. It's even more true for me when they are factory methods. I'll try to find a more complete description of the standard conventions. – Dici Jun 26 '19 at 09:07

score 5 · Answer 2 · edited Dec 06 '13 at 13:01

5

Personally I use option 2 (static fields and methods prior to instance elements and constructs). To me this makes sense when scanning a file because from a user of a class, I can access the static stuff without needing an instance. Therefore it is nice to see them prior to the constructors because I don't care about constructors when using static stuff.

edited Dec 06 '13 at 13:01

Tomislav Nakic-Alfirevic

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answered Sep 23 '11 at 14:36

John B

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counterargument is that 99% of the time you use instance so having static and inner classes stuff out of the way is much better at the bottom – Enerccio Dec 11 '21 at 11:39
@Enerccio I am not sure I agree with your assertion. I find that many times classes are either all-status utilities, all instance method classes or when there is a mix, the static methods tend to be the entry points (like factory methods). So I would propose that when there is a mix, you generally start with the static methods then use the instance methods once you have an instance. – John B Dec 11 '21 at 13:02
There is also using static methods for optimization – Enerccio Dec 12 '21 at 14:04

score 3 · Answer 3 · answered Sep 23 '11 at 14:38

Just for the record, this is from the GWT article you linked:

We acknowledge that plenty of great approaches exist out there. We're simply trying to pick one that is at least somewhat consistent with Sun's Java coding conventions...

So the style they use

is proposed for GWT not for general usage
deviates somewhat from the standard conventions
is acknowledged to be one of many good standards

So I'd say, if there's no reason not to stick with your current conventions, why change them?

score 2 · Answer 4 · answered Sep 23 '11 at 14:35

The Java Code Conventions suggest the following (which is basically what you already do):

Class (static) variables: First the public class variables, then the protected, then package level (no access modifier), and then the private
Instance variables: First public, then protected, then package level (no access modifier), and then private
Constructors
Methods: These methods should be grouped by functionality rather than by scope or accessibility. For example, a private class method can be in between two public instance methods. The goal is to make reading and understanding the code easier.

score 0 · Answer 5 · answered Sep 23 '11 at 14:30

I don't know, but for what it's worth, I do what you do. Constructors on top, methods grouped by functionality (with no regard to staticness) below. Static methods tend to group.

The exception is static factory methods that I intend for you to use instead of constructors -- if so, they are before constructors, and the ctors are private/protected.

score 0 · Answer 6 · answered Sep 23 '11 at 14:35

0

It's all a matter of preference, of course...

Your convention is more consistent with the default ordering in Javadoc (i.e. static and non-static methods mixed together). This is what I normally do, too.

However, inner classes are often placed at the bottom of a class as they are often 'secondary' or 'helper' classes, and it seems odd to put them before the main meat of the outer class.

answered Sep 23 '11 at 14:35

DNA

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Yeah that's right. I also put inner classes at the bottom of a class. – Heejin Sep 23 '11 at 14:39

score 0 · Answer 7 · answered Sep 23 '11 at 14:35

0

I put static initializers and methods before constructors, so I guess I'm following your citation.

Why the discomfort? It seems like a small thing.

answered Sep 23 '11 at 14:35

duffymo

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Java coding convention about static method

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