ANTLR 4.7.1生成的解析器中的问题

Question

I created a grammar called goal.g4

Then, from terminal (on a mac) I launched "java -cp "antlr-4.7.1-complete.jar" org.antlr.v4.Tool goal.g4 -listener -visitor" that terminates correctly.

Then I use the following java code:

input = new ANTLRInputStream(fis); /* where fis is a FileInputStream */
goalLexer lexer = new goalLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
goalParser parser = new goalParser(tokens);
parser.start();

my point is: how to retrieve the ParseTree object from the parser? As suggested I replaced the init() method with the start() methods. However eclipse tells me that parser.start() does not exist...

How do I solve this? Thanks Luca

Answer 1

Look in your grammar. You have to identify the start rule you want to go with. Usually the start rule is near the top of the file and/or is one of the few (or only one) that is not called by any other rule.

Whatever rule you choose it will return a parse tree context, which forms the root of your parse tree, eg

ParseTree tree = parser.start();