Checker Framework GitHub

The tool analyzes Java source to verify and enforce type qualifiers defined by the Checker Framework. It supports nullness, mutability, and other qualifiers through annotations or inference, and integrates with Gradle/Maven builds and GitHub Actions to surface issues in development and CI pipelines. By analyzing data flow and type constraints, it identifies violations such as potential NPEs, unintended aliasing, or contract violations.

Conceptual workflow: provide inputs (source paths, classpath, and annotation libraries); the analyzer builds an AST and a qualifier lattice, processes annotations, propagates constraints through statements, and reports violations with precise file, line, and checker information. It can export SARIF or JSON reports for automated tooling.

Beneficiaries include engineering teams with large Java codebases, library authors, and CI engineers requiring reproducible checks. Unique value includes pluggable checkers, standard qualifiers, and compatibility with common build tools, enabling scalable enforcement across modules.

Core features and use cases: standard and custom checkers, incremental and full analyses, SARIF export, and easy integration into CI. Use cases include migrating to strict null-safety, auditing dependencies for qualifier compliance, and enforcing contracts across multi-module projects.