scannergen-backend-java.md

Scanner Generator Backend: Java

This backend outputs a scanner as Java source code. See scanner generator backends for what every generated scanner does and parser generator backend: Java for the parser side.

It targets Java 17.

--backend-java-package-name sets the package the file declares, which defaults to parser.

The scanner is the Scanner class, its tokens are the nested Scanner.Token enum, and the nested Scanner.TokenSkipper wraps a scanner to drop the tokens marked for skipping. Both implement TokenSource, which is what a parser reads its tokens through. Lexemes are a ByteBuffer over the source rather than a copy of it.

Example

examples/calculator/java/ is a calculator built on this backend. Its scanner was generated with:

golr scanner \
  --frontend golr \
  --frontend-file-path calculator.golr \
  --backend java \
  --backend-file-path parser/Scanner.java