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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I think the calls to initParser should either be to Start or to init.

In this example, javaacc are checking the file structure only. Parsing functions can take in parameters, return results, and invoke blocks of arbitrary Java code. Thank you very much. One way to do this is to use a very large integer value such as the largest possible integer as follows:. Let us suppose that there is a good reason for writing a grammar this way maybe the way actions are embedded. In my journey I did find, however, that there is a lack of a gentle introduction into JavaCC.

So far, we have described the default lookahead algorithm of the generated parsers.

An Introduction to JavaCC – CodeProject

Tutoorial grammar files yield more modularity, and are easy to read, modify, or write when compared to a handwritten Java parser, and hence it saves a lot of time and effort. Rutorial the grammar file and run the appilication. A common prefix is: In my experience, if parsing fails by either one of these, I need to abort the operation. In this section, we define the package, all imports, and the parser class.

This determination in its most general form can be quite time consuming.


Note that the generated parser code contains a constructor that accepts the reader. The next input character is a ‘c’, so we are OK now. This first article will be a quick getting started guide aimed to get you up and running quickly. One of the features of JavaCC that I tutoial like, is that the generated parser has no dependency on javacc.

Erik’s Java Rants

You can use it to create your own custom parser. JavaCC produces 7 Java files in the output. The parser itself throws two types of Throwables depending on the type of problem that is encountered.

You must remove left recursion before writing your grammar rules in JavaCC. DemoParser is our main entry point for interacting with the generated parser. If lexical analysis fails, it will throw a Tutorixl.

If ttuorial are using Eclipse, then there are free JavaCC plug-ins available. Finally, we add a single parser rule to our grammar file: This means we have successfully matched the string “abc” to the grammar. Most parser generators support the BNF production rules for specifying the sequence of token kinds in an error free output. Type the command “javacc demogrammar. I have used a stop sign to indicate directories that should not be modified, because they are generated.

If these guys would at least organize the material they already have on the project site into a readable form instead of a MiniTutorial on X and MiniTutorial on Y.

An Introduction to JavaCC

And after that, looking at actual grammars and trying to figure out why they work the way they do is probably the last step. This tutorial refers to examples that are available in the Lookahead directory under the examples directory of the release.

Lookahead tutorial We assume that you have already taken a look at some of the simple examples provided in the release before you read this section.


You specify a language’s lexical and syntactic description in a JJ file, then run javacc on the JJ file. It is empty for now, but you could specify manifest entries here if you wanted to. So, we can simply iterate the names and print them, no need to use Token Objects.

In this example, it defines the structure of the file as: The demo uses two jar files found in the lib directory 1 javacc. Unit Testing In this section I will demonstrate how we can write unit tests for lexing and parsing. I do tutoral acquainting oneself with the theory behind parsing, when tutroial with parser generators. However, it makes your application robust and error free, particularly when dealing files with a specific format.

In the root of the project you can see the ant build. The general approach is to replace rules of the form.

Consider the following grammar file Example2. There are also similar constants for the column number. But the tree is really there. Using JavaCC for such problems is overkill and will cause mor e problems than is solves. In the build file target javacc generates the parser, target compile-main compiles the parser, lastly compile-test compiles the unit tests. We have shown you examples of two kinds of choice points in the examples above – “exp1 exp Erik Lievaart Javaccc, I wanted to write tutirial own parser for a hobby project.

My vote of 5 Vinod Viswanath Aug 8: Winston Chen 3, 11 42 If more than one are present, they are separated by commas.