See the JavaCC documentation for details. Also see the mini-tutorial on the JavaCC site for tips on writing lexer specifications from which JavaCC can generate. At the end of the tutorial, we will parse a SQL file and extract table specifications ( please note that this is for an illustrative purpose; complete. In this first edition of the new Cool Tools column, Oliver Enseling discusses JavaCC — the Java Compiler Compiler. JavaCC facilitates.

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Download and install a plug-in Google for easy-javacc The developerWorks tutorials that zimbu indicated is pretty good; it does some more advanced stuff. You can try running the parser generated from Example3. You’d make a nice function called parse perhaps, and call that from your own code.

I think the calls to initParser should either be to Start or to init. The demo uses two jar files found in the lib directory 1 javacc. When we have such a problem in the general case, we conclude that we may have made a bad choice somewhere. Consider the following grammar file Example2. In the majority of situations, the default algorithm works just fine.


After invoking Javacc on the grammar file demogrammar. The return type is the intended return type from javac BNF. These grammar files are named with the extension. We initialize the parser with an InputStream or a Reader, so we can easily parse all sorts of sources.

It is also possible to use a catch all token, which will turn all TokenMgrErrors into ParseExceptions. The ” ” character is tutoria, to separate tokens. Please Sign up or sign in to vote.

Erik’s Java Rants

At the end of the tutorial, we will parse a SQL file and extract table specifications please note that this is for an illustrative purpose; complete SQL formats are not supported. For parsing the above file, our grammar file looks like the following:.

I’m about halfway through the Book now: These targets are called implicitly through dependencies where needed. And you’re good to go. I was able to create a query language for our application in a few days with basically no previous experience with jacacc. This is because a the java files depend on the parser and it hasn’t been generated yet.

As mentioned earlier, special tokens are those which don’t contribute any meaning, but are still informative, such as comments. It definitely helps you understand the structure and syntax of JavaCC!


A step by step approach is desired while dealing with a complex file. The standard interpretation is that it is bound to the inner if statement the one closest to it.

Getting started in JavaCC

As we have discussed an overall idea of JavaCC operation, now we can add jvacc more items to the file to parse. I named the parser rule for the demo project parseFile in the section above. String image int kind int beginLine int endLine The image attribute of the Token class contains the raw token as found in the InputStream. Throws exceptions on errors in lexical analysis.

An Introduction to JavaCC

It starts you off making a simple adder, then calculator. If you are using Eclipse, then there are free JavaCC plug-ins available.

Option 1 You can modify your grammar so that the warning messages go away. Tokens are enclosed within angle brackets. Note that the generated parser code contains a constructor that accepts the reader.

JavaCC produces 7 Java files in the output.