I am looking for a parser generator for Java that does the following: My language project is pretty simple and only contains a small set of tokens.
Output in pure R
Maybe you're looking for parser combinators instead of parser generators? See this paper and JParsec.
It's a really bad idea to edit generated parser code--it's a lot easier to edit the grammar file and then recompile it. Unless you're doing it for educational purposes, in which case ANTLR prides itself in generating pretty readable code for such a powerful parser generator.