Catching (and keeping) all comments with ANTLR

Question

I\'m writing a grammar in ANTLR that parses Java source files into ASTs for later analysis. Unlike other parsers (like JavaDoc) I\'m trying to keep all of the comments. This

Answer 1

Section 12.1 in "The Definitive Antlr 4 Reference" shows how to get access to comments without having to sprinkle the comments rules throughout the grammar. In short you add this to the grammar file:

grammar Java;

@lexer::members {
    public static final int WHITESPACE = 1;
    public static final int COMMENTS = 2;
}

Then for your comments rules do this:

COMMENT
    : '/*' .*? '*/' -> channel(COMMENTS)
    ;

LINE_COMMENT
    : '//' ~[\r\n]* -> channel(COMMENTS)
    ;

Then in your code ask for the tokens through the getHiddenTokensToLeft/getHiddenTokensToRight and look at the 12.1 section in the book and you will see how to do this.