JFlex Generator

About This Tool

Generates Java JFlex scanners from lexical specs to accelerate lexer development and ensure reliable integration in Java parsing pipelines. The tool targets language tool developers, compiler engineers, and build teams who require repeatable, testable lexical analyzers. It enforces JFlex-compatible syntax, macro expansion, and proper handling of character classes and ignore patterns. Outputs are deterministic, reproducible, and easy to integrate into standard Java build workflows.
Conceptually, the generator parses the lexical spec, resolves macros, constructs a finite automaton from ordered token rules, and emits Java sources following established JFlex conventions. It supports macros, ranges, and Unicode options, with capabilities to set package, class name, and output path. The produced sources can be compiled with Maven or Gradle and tested with representative input streams.
Audience benefits include teams building DSLs or language tooling, IDE developers adding lexers, and projects requiring a reproducible Lexical Analysis component. Unique value lies in strict validation, informative error reporting, and clean, ready-to-compile sources that minimize manual lexer coding. Typical use cases include rapid lexer prototyping, rebuilding lexers after grammar changes, and enforcing consistency across modules.
Core features include syntax validation, macro expansion, rule ordering, conflict hints, and generation of a standard JFlex-compatible scanner. It outputs Java source files, supports optional packaging metadata, and provides clear messages to guide fixes. The tool differentiates itself by delivering repeatable generation, strong error visibility, and seamless integration with common Java build systems.

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