feat: add support for cognitive complexity analysis in Java

[askpt]

Summary

Add support for analyzing and displaying Cognitive Complexity metrics for Java files using the Visual Studio Code extension.

Motivation

Java is one of the most popular languages in modern software development. Supporting Java will significantly broaden the reach and applicability of this extension, enabling teams to measure cognitive complexity across polyglot codebases.

Acceptance Criteria

• Cognitive Complexity analysis is available for Java files (.java).
• Analysis aligns with SonarSource's Cognitive Complexity specification as applied to Java syntax.
• CodeLens overlays show complexity scores above each function/method in Java files, using familiar color coding (green/yellow/red) based on user-configured thresholds.
• Configuration options (thresholds, enabling/disabling CodeLens, etc.) are updated to allow/disable Java analysis, as done for other supported languages.
• Automated tests verify the accuracy of Java complexity analysis logic.

Out of Scope

• Non-Java language changes not directly required for enabling Java support.

Additional Notes

• Implementation should utilize a language parser such as Tree-sitter or equivalent to enable accurate metric calculation for Java code, mirroring techniques and abstractions used for C# and Go analyzers.
• Be mindful of Java-specific language constructs (lambdas, nested classes, anonymous classes, etc.).

[github-actions]

🎯 Agentic Issue Triage

Summary: Feature request to add Cognitive Complexity analysis for Java (.java) files, following the same patterns already used for C#, Go, JavaScript, and TypeScript.

This is a well-scoped, high-quality request from the repo owner — no spam or duplication detected. A similar issue (#237) is open for Python support.

📐 Implementation Approach

The codebase is highly modular and adding Java support follows a clear pattern. Here's the full checklist:

Sub-tasks

• Install tree-sitter-java npm package as a production dependency

  npm install tree-sitter-java

  Check [npmjs.com/package/tree-sitter-java]((www.npmjs.com/redacted) for the latest version.

• Create src/metricsAnalyzer/languages/javaAnalyzer.ts
  Model it after goAnalyzer.ts or csharpAnalyzer.ts. Key Java node types to handle in the Tree-sitter AST:

  • method_declaration, constructor_declaration — function boundaries
  • if_statement, while_statement, for_statement, enhanced_for_statement, do_statement — +1 each (nested = +nesting)
  • catch_clause, switch_expression, switch_statement — +1
  • binary_expression with && / || — boolean sequence nesting
  • lambda_expression, anonymous_class_declaration, local_class_declaration — structural / nesting increments
  • ternary_expression — +1

• Register java in languageAnalyzers inside metricsAnalyzerFactory.ts:

  java: createAnalyzer("./languages/javaAnalyzer", "JavaMetricsAnalyzer"),

• Add activation event in package.json:

  "onLanguage:java"

• Add java keyword to package.json keywords array for discoverability.

• Add a samples/Test.java sample file for manual validation.

• Write unit tests in src/unit/ mirroring the existing unit test patterns for other languages.

⚠️ Java-Specific Complexity Gotchas

• Lambdas (x -> x + 1) count as a structural complexity increment (like anonymous functions in JS) and also add a nesting level.
• Anonymous classes and local classes defined inside methods increase nesting.
• Method chaining (fluent APIs) — typically not a complexity increment per SonarSource spec.
• switch expressions (Java 14+) vs classic switch statements — both increment complexity; the tree-sitter grammar distinguishes these as switch_expression and switch_statement.
• try/catch — each catch_clause adds +1, finally does not.
• instanceof pattern matching (Java 16+) — not a complexity increment per spec.
• Refer to the [SonarSource Cognitive Complexity White Paper]((www.sonarsource.com/redacted) for authoritative guidance on Java examples.

🔗 Useful Resources

• [tree-sitter-java npm package]((www.npmjs.com/redacted)
• tree-sitter-java GitHub — browse grammar rules for Java node type names
• [SonarSource Cognitive Complexity White Paper]((www.sonarsource.com/redacted)
• Existing Go analyzer — best reference for a similar imperative language
• Existing TypeScript analyzer — reference for lambda/arrow function handling

🧪 Testing Strategy

Use the unit test pattern established in src/unit/ for other languages. Cover at minimum:

1. Simple method with no control flow → complexity = 0
2. Single if → 1
3. if/else if/else → 2 (each branch)
4. Nested if inside loop → 1 (loop) + 1+1 (nested if) = 3
5. Lambda expression inside method → structural + nesting
6. Anonymous class → structural + nesting
7. try/catch with multiple catch blocks
8. switch statement with multiple cases
9. Recursive method call — check whether recursion bonus applies per spec

Generated by Agentic Triage for issue #238 · ● 284.7K · ◷

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