JavaCC

JavaCC, the Java Compiler Compiler, is a parser generator for Java. It reads a grammar specification and produces Java source code for a lexical analyzer (scanner) and a parser, enabling the creation of compilers, interpreters, and other language processing tools. The generated code integrates with standard Java projects and exposes a parse method that processes input and reports syntax errors.

A JavaCC grammar is typically written in a .jj file. It contains sections that define tokens (regular expressions for lexical elements) and the grammar productions (nonterminals with their productions). Semantic actions written in Java can be embedded within productions to build parse trees, perform semantic checks, or generate intermediate representations. JavaCC supports lookahead, backtracking, and syntactic predicates to resolve ambiguities during parsing, and it can interoperate with additional tooling to construct abstract syntax trees.

For tree construction, users commonly employ the JJTree tool in conjunction with JavaCC. JJTree augments a grammar to produce an abstract syntax tree by creating explicit node classes and wiring actions to AST nodes. The combination is widely used in compiler projects and other language-processing tasks where structured representations of source code are required.

Workflow generally involves writing a grammar, running the JavaCC tool on the grammar file to generate Java source files, compiling those files within a Java project, and then instantiating the generated parser in the application to parse input. JavaCC is distributed as open-source software and has been maintained for many years as a mature option for Java-based language processing needs.