Add checkstyle rule UnusedLocalVariable, UnusedLocalMethodCheck

[Pankraz76]

Add Checkstyle Rules: UnusedLocalVariable and UnusedLocalMethod

Rationale:

Our project currently leverages Checkstyle to enforce code quality, particularly by identifying and preventing unused imports. This practice helps to keep our codebase clean and efficient. Extending this philosophy, we aim to minimize overhead and eliminate obsolete (dead) code throughout the project. Introducing the UnusedLocalVariable and UnusedLocalMethod Checkstyle rules directly supports this goal.

Benefits:

• Reduced Overhead: Unused local variables and methods, while seemingly harmless, can contribute to unnecessary bytecode and potentially impact performance, however subtly. By flagging and removing them, we reduce the overall footprint of our application.
• Avoidance of Unnecessary Code (Dead Code): Dead code, by definition, serves no purpose. It can clutter the codebase, making it harder to understand and navigate. Identifying and removing unused local variables and methods prevents the accumulation of such dead code.
• Increased Maintainability: A cleaner codebase, free of unnecessary elements, is inherently easier to maintain. Developers can focus on relevant code, reducing the cognitive load and the risk of introducing bugs in unrelated sections. Removing dead code simplifies refactoring and future modifications.

Implementation:

By adding these two Checkstyle rules to our configuration, the build process will automatically flag any instances of unused local variables and methods. Developers will then be prompted to either remove these elements or justify their existence. This proactive approach ensures that our codebase remains lean and maintainable over time.

References:

• https://checkstyle.sourceforge.io/checks/coding/unusedlocalvariable.html
• https://checkstyle.sourceforge.io/checks/coding/unusedlocalmethod.html

Related Examples:

• Pull #34814: apply RemoveUnusedPrivateFields #34814
• Pull #34809: apply RemoveUnusedLocalVariables #34809
• Pull #34808: apply RemoveUnusedPrivateMethods #34808
• Pull #34816: Add checkstyle rule UnusedLocalVariable, UnusedLocalMethodCheck #34816