Static and Dynamic Code Inspection for Reducing Java Backend Code Corruption

The article introduces the problem of code bloat in growing Java backend projects, where useful, unused, low‑frequency, and experimental code accumulate, increasing maintenance cost and risking corruption that may eventually require a full rewrite.

It outlines a three‑step static code inspection process: (1) using IntelliJ IDEA's built‑in inspection to find unused classes, variables, and methods; (2) installing and configuring the PMD plugin with custom rulesets to detect empty blocks, unused imports, and other code smells; (3) employing CPD for duplicate‑code detection. Advantages and drawbacks of each tool are discussed, including false positives from Spring @Value, Lombok @Data, and constructors.

The article provides an example PMD <?xml version="1.0"?> <ruleset name="myruleset" xmlns="http://pmd.sourceforge.net/ruleset/2.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd"> <description>My ruleset</description> <!-- Empty catch block --> <rule ref="category/java/errorprone.xml/EmptyCatchBlock"/> <!-- Empty finally block --> <rule ref="category/java/errorprone.xml/EmptyFinallyBlock"/> <!-- Empty if statement --> <rule ref="category/java/errorprone.xml/EmptyIfStmt"/> <!-- Unused local variable --> <rule ref="category/java/bestpractices.xml/UnusedLocalVariable"/> <!-- Unused private field --> <rule ref="category/java/bestpractices.xml/UnusedPrivateField"/> <!-- Unused private method --> <rule ref="category/java/bestpractices.xml/UnusedPrivateMethod"/> <!-- Avoid importing java.lang --> <rule ref="category/java/codestyle.xml/DontImportJavaLang"/> <!-- Duplicate imports --> <rule ref="category/java/codestyle.xml/DuplicateImports"/> <!-- Unused imports --> <rule ref="category/java/bestpractices.xml/UnusedImports"/> </ruleset> showing how to configure checks for empty blocks, unused variables, and import issues.

For dynamic analysis, the article describes setting up a JaCoCo pipeline on JD’s CI system: downloading the JaCoCo agent, adding it to JVM options, running the pipeline, and reviewing coverage reports to identify code that is never executed and can be safely removed.

Conclusions recommend combining PMD + CPD for static inspection and JaCoCo for dynamic coverage, noting that while static tools can automatically flag many dead code fragments, final decisions still require manual review, especially for public APIs and complex logic.