Writing Java codes conforming to coding standard

Recently, I was doing some cleanup to one of my current Java project. I find there are many codes which are not conforming to the Java coding standard. So I list them here and hope that people can improve your codes and write maintainable codes.

Format source code and manage imports in Eclipse

Eclipse provides functions of auto-formatting and imports management, you can use following shortcuts to use these functions.

• Ctrl+Shift+F --> Format source code
• Ctrl+Shift+O -- Manage imports and remove unused import statements

In addition to manually execute these two functions, you can also let Eclipse auto format your source codes and manage your imports when you save the source codes. In order to achieve this, go to Windows->Preference->Java->Editor->Save Actions, and select the Perform the selected actions on save, check Format source code and organize imports.

Avoid multiple return statements in methods(multiple exit points)

In your method, make sure there is only one exit point, don't put multiple return statements in a method.

For example, the following code snippet is not recommended.

The above code can be rewritten as

Simplify if-else

We may often need to write some methods which take only one argument and check on that argument and return some value according to the argument.

For example the isEligible() method above :

We can use remove if-else

Don't create new instance for Boolean, Integer and String

Avoid creating instance of Boolean, Integer and String with new, use Boolean.valueOf(true) to replace new Boolean(true). These two methods have the same effect but have different performance.

Use {} around code block

Don't forget to put {} around code block (such as if, while,for), this can reduce code confusion and avoid introducing new bugs when changing codes in the future.

Following code snippet is not recommended:

We should write

Declare method parameter as final

Declare method parameter as final whenever possible, by doing so, when you change the value of the parameter accidently, the compiler may throw an error. Also, the machine codes generated with final will also be optimized.

Give CAPITAL name for public static final variables

Always use CAPITAL name as public static final variable name, this can distinguish what is constant and what is local variable.

Following is not recommended:

Follwong is recommended

Merge multiple if statements

The following code snippet

can be rewritten as

Don't forget to add default statement for switch

Always add a default statement for switch

Avoid repetitively using the same string literal, create a constant instead

If you need to use the same string literal in many places, then the wise way is to create a string constant.

For example

we can create a constant to replace "My Application"

Writing correct program is just part of programming, we should develop good programming habits in order to improve coding efficiency. Writing correct codes is not enough, we have to consider maintainebility and readability because frequently other people may maintain our codes. We as programmer don't want to hear something "What a stupid programmer" from others, right? So writing codes conforming to standard  both for yourself and for others.

Reference : http://www.oschina.net/question/100267_70351