Java Comments Best Practices Example

Comments are an important part of writing code not only in Java but whatever programming or scripting language you use. At the same time, this is one of the most abused things as well. Both writing no comment and writing too much comment is bad and this has been highlighted by many software gurus e.g. Robert C. Martin in his classic book Clean code. There is a whole chapter dedicated to How to write comments and finding the pros and cons of a comment. This article is my learning in the same direction, here I am going to share with you guys some 0f the rule and best practices I follow while writing comments.

Before that let's first see what is the purpose of having a comment in the code? Why do we need comments, isn't writing code is enough. Some of the people I have met always argue that we are getting paid for writing code and not comment :).

Anyway, in my opinion, we all agree with each other that software spends only 10% time of its life in development and rest of 90% in maintenance. This 90% part of maintaining the code is where comments can help you immensely.

Since no single developer stays till the whole life of any product or software and its often new people, who work of already written code. These are the people who read the code and not aware of why a certain piece of code has been written, here comments can help them to understand code quickly and believe me you will get lot of roses from that fellow developer :).

Anyway long story short here are some of the things I try to follow while writing code:

10 tips on writing code comments

1) Readability

Focus on thereadability of code; assume that you don't have comments to explain the code. Give your method, variables, and class meaningful name.

2) Don't write what code is doing

There is no point to write what the code is doing, this should be left for the code to explain and can be easily done by giving class, variable, and method meaningful names. For example:

//calculates square root of given number

//using Newton-Raphson method

public void          abc(int a){

       r = a / 2;

       while ( abs( r - (a/r) ) > t ) {

       r = 0.5 * ( r + (a/r) );

       }

       System.out.println( "r = " + r );

}

The above code is calculating square root using theNewton-Raphson method and instead of writing a comment you can just rename your method and variable as follows:

public void          squareRoot(int num){

       root = num/ 2;

       while ( abs(root - (num/ root) ) > t ) {

       r = 0.5 * (root + (num/ root));

       }

       System.out.println( " root = " + root );

}

3) Explain Logic or Reason

Always write why you are writing this piece of code, why you are writing this piece of code because this information is not visible until you write them in comments and this is critical to identify any bug or behavior with changing the business environment.

4) Follow Established Standards

If you are writing core libraries which will be used by different project and with different teams. Follow Javadoc commenting style and document all assumptions and precondition for using your API. Joshua Bloch has also mentioned about writing Java-doc comment in his classic Effective Java, which is worth knowing.

5) Include JIRA Number

It makes sense to include JIRA Number and description on comment, especially if you are modifying an existing piece of code as part of maintenance. This I found extremely useful while comparing different version of code in CVS or SVN. This gives you clear idea why that particular code has been added and whether issue is because of that piece of code or not.

6) Keep it Short

Always try to finish your comment in as few words as possible, one-liner comment is best until it's explaining the"Why" part and can't be replaced by code itself. Nobody likes or has enough time to read longer comments.

7) Don't put already available information

Don't write a story in the comment as your name, employee id, your department, etc because that information can be obtained from Git commit data in case someone wants to know who has made this change.

8) Don't commit the Code without comment

Always put comments while committing code in the source control repository and especially why you are adding this piece of code if possible include JIRA or QC Number so that anyone can refer JIRA for complete details.

9) Create a Comment Guideline for Team

If you want upcoming developers to follow certain standards or inform about certain things then include them in the beginning of your class as a comment. E.g. suppose if you are writing a serializable class in java then it's good to put a serializable alert stating that any new fields added in this class must implement a Serializable interface in java or make it transient etc.

10) Avoid Duplicate Comment

There is no point putting duplicate comments on each and every git commit. Since your code is changing, try to put what the commit is doing instead of copying the blanket and duplicate comments from the previous commit.

That's all from me on code commenting, please share the standard, best practices, or your experience with writing comments on code. I believe these are the areas in which a junior developer or even we can improve and it's only possible from learning which each mother's experience.

Last but not least give your code to the fellow developersto understand as part of code review and ask him how much he understands it.


Happy weekend :)

peterswasking.blogspot.com

Source: https://javarevisited.blogspot.com/2011/08/code-comments-java-best-practices.html

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