Java (Base language)¶

To learn more about advanced Java topics such as the Java virtual machine, collections language, and many more topics, visit baeldung.com ⧉.

Refactoring.guru ⧉ has information about general code smells.

Be aware of common Java gotchas ⧉.
Avoid acronyms and abbreviations that may not be clear to others.
Name methods and variables after what they mean. Before giving a name, consider the responsibility of that piece of code (Naming 101: A Programmer's Guide on How to Name Things ⧉).
Return empty collections instead of returning null elements (reference ⧉). It saves the efforts needed for testing on null elements.
Efficiency: Use StringBuilder or StringBuffer ⧉ for String concatenation
Refactor your code regularly, especially when your classes or methods become too big (Rule of 30 – When is a Method, Class, or Subsystem Too Big? and Avoid basic style errors ⧉)
Remember to test the parameters of public methods for illegal values. These methods shouldn't crash because of a NullPointer.
Order class members by scope from private to public (Ordering Class Members by Scopes and Separate public and private members ⧉)
Minimize the accessibility of class members. It enforces information hiding or encapsulation ⧉.
Avoid hardcoded values.
Use lazy initialization if performance is critical, or use caching ⧉ if necessary.

Utility and Helper Classes¶

Utility class: They include only static methods and are stateless. Don't create an instance of such a class.
Helper class: They can be utility classes, or they can be stateful or require an instance. It can be any class whose design is to aid another class.
Try to make the name of the utility or helper class more specific (e.g., AdministrationHelper, LoginHelper instead of Helper).

If you use functional interfaces, use the standard Java ones. If you want to understand the functional style, consult the page: Understand the functional style ⧉.
If you want to use newer Java features, look at Modernize old code ⧉.
Have a look at common sources of complexity ⧉.