Software Development Best Practices----

Coding Standards & Maintainable Code

Ankur GoyalEmail: ankur.fbd@gmail.com

for(j=0; j<array_len; j+ =8){ total += array[j+0 ]; total += array[j+1 ]; total += array[j+2 ]; /* Main body of total += array[j+3]; * loop is unrolled total += array[j+4]; * for greater speed. total += array[j+5]; */ total += array[j+6 ]; total += array[j+7 ]; }

Warm up

for(j=0; j<array_len; j+ =8){ total += array[j+0 ]; total += array[j+1 ]; total += array[j+2 ];/* Main body of loop is unrolled for greater speed total += array[j+3]; total += array[j+4]; total += array[j+5]; */ total += array[j+6 ]; total += array[j+7 ]; }

Isn’t it better ?

What is it you expect, to get out of this Session?

Participant’s Expectations

Setting Expectations Right

• What this session is about?– Identify & appreciate the importance of Coding

Standards – Few examples– Introduction to standard supporting tools

• What this session is not about?– Coding Tutorial– Details on coding standards

Maintainability• Maintainability is the ease with which a product

can be modified in order to:– correct defects or their cause– meet new requirements– cope with a changed environment– e.g. iOS 5 to iOS 6, windows 7 to windows 8

Write simple, self-documenting code that is pleasant to revisit even after months.

Coding Standards• Coding standards are guidelines for code style and

documentation.

• The purpose is that any developer familiar with the guidelines can work on any code that followed them.

• We need to write code that minimizes the time it would take someone else to understand it --- even if that someone else is you.

Why Have Coding Standards?

• Reducing the cost of software maintenance is the most often cited reason for following coding standards.

• ~80% of the lifetime cost of a piece of software goes to maintenance.

Is this really necessary ?• YES. To all programmers, even if there is only one developer

on the project.

• Because:

– Most of the time software is not maintained by the original author.

– If everyone follows the standards, you feel comfortable using your colleague's code, because it seems like your own code.

hmmm really ?– Estimations are approved considering an average programmer

who follows coding standards.

– Not following coding standards will lead to review comments & thereby rework, which in turn will lead to effort variation.

– Since most of the time client delivery dates are fixed hence it all leads to extra hours spent in office -> more time -> more money.

– It’s a vicious circle, only way out is following coding standards.

FEW EXAMPLE

S

Using constants on LHS

• Constants should always be used on left hand side of equality operator

• Avoids invalid assignment

• Avoids null pointer exceptions

Using constants on LHS

T h i s c o d e c a n c a u s e N u l l P o i n t e r E x c e p t i o n i f p a s s e d a r g u m e n t ‘ i n p u t ’ i s n u l l

R i g h t A p p r o a c h

Indentation

• Gives an indication of scope though doesn’t affect program

• Must for maintainability & readability of code

ExampleCompare

- Easier to Read

- Easier to Understand

- Easier to maintain

To

Pressing “Ctrl+shift+f” in eclipse formats source file (set up your formatting style in Window|preferences | java | code style | formatter)

Commenting Code

• Document WHY & WHAT along with HOW.

• Comments should - Clearly demonstrate the function of the code, both to yourself and to other developers

• Comments should NOT be - Too long- Overcomplicated

ExampleCompare

ExampleTo

Comments are not about how much you write Comments should add illustration to the code for maintainability

Naming Variables

• Variable names are often thought to be less important but they are vital to understanding certain pieces of code.

• In the majority of programming languages, variables can be assigned almost any name.

ExampleCompare following:

To:

Trade off is generally between meaningfulness & shortness, rule of thumb is, always give priority to meaningfulness.

Instance Creation

• Do not create instances as far as possible.

• creation of new instance is avoided in the internal part of loop.

ExampleCompare

Instance creation in loop, this may lead to out of memory error…

To

Instance Creation

• Use valueOf() instead of new().

• valueOf() provides value from cache while new() creates new instance.

Example

use

instead of

Cast

• As much as possible cast must be enclosed in condition statement of instanceof.

Use instanceof()

This may lead to classcastexception

Use instanceof to avoid classcastexception

Unreadable Code

• Write a code that can be understood by any average programmer.

• This helps in maintainability & readability of code.

• Helpful in understanding time critical projects

Example

Compare

To

Programmer’s expertise is not in writing complex code, expertise is to write a code which is easy to understand & maintain.

String Concatenation

• Use StringBuffer and StringBuilder for String concatenation operations.

• String is immutable hence creates new objects whenever the value is changed

• Use StringBuffer if application is multithreaded & synchronization is required

• Use StringBuilder elsewhere.

ExampleInstead of

Use

Or

String object is immutable whereas StringBuffer/ StringBuilder objects are mutable

REPOSITORY COMMENTS

• Often it is observed that repository comments do not get the attention they deserve.

• Repository comments should convey the changes committed along with applicable references e.g – If bug is fixed mention fixed bug ID– If any CR is implemented mention CR number/name– If review comments are fixed mention review plan id

ExampleFollowing are some of the real svn repo comments:

SVN repo comments serve purpose of maintaining code revision history, pay respect to this fact & spend some time to write useful comments

Coding Standard & Best Practices Tools

• CheckStyle– makes sure that everyone in the team write code in a similar

manner– is the glue that enables people to work together and to free up

their creativity instead of spending time and energy at understanding inconsistent code.

• PMD– reminds you of bad practices such as:

• Catching an exception without doing anything• Suboptimal code - wasteful String/StringBuffer usage• Duplicate code - copied/pasted code means copied/pasted bugs

Recap• The purpose is that any developer familiar with the

guidelines can work on any code that followed them.• Following coding standards saves both time and

money.• Standardize early - the effort to bring your old work

into the standard will be too great otherwise.• Document every time you violate a standard.• Industry Standards > organizational standards >

project standards > no standards.

THANKS !!!

Guidelines & practices mentioned in this slide were just a tip of iceberg, there is no hard & fast rule regarding guideline & they generally differ on basis of domain, technology used & clients’ requirement etc.

Purpose of this presentation was to encourage habit of following standards by identifying importance of the same.

Finally, following guidelines & adhering to standards is responsibility of each individual.

Conclusion