JavaCC comes with a built in tree builder, JJTree. One of the nice bits about JJTree is that it will generate a visitor implementation so you can easily traverse the abstract syntax tree. However, the interface that JJTree generates looks like this:
Since that second parameter is an Object, you're always downcasting if you want to use it. For example, if you're passing around a Map, you'll need to do something like this in your visitor:
But thanks to Paul Cager, JJTree has a new
VISITOR_DATA_TYPE option. Just set it like this:
With this option in place, the generated visitor interface looks like this:
And now your visitor implementation can look like this - no cast necessary!
Note that you'll want to declare a fully-qualified type, otherwise you'll need to go back and fill in the import statements. So it's more readable, more type-safe, and it probably yields a small runtime performance improvement due to the eliminated cast. You can grab a javacc.jar built from CVS here if you want to give it a whirl. Props to Paul for this and his other recent bug fixes!
Using JavaCC or JJTree? Get the JavaCC book!