how to create a new syntax in java?

What are the steps to use ANTLR to create an abstract syntax tree of Java source code and then walk the tree?

• I have successfully installed antlr and the java.g4 grammar. Now, I want to take a java source code file as an input and create a AST and then walk it (in netbeans). How do I do this?

• Answer:

  Unlike ANTLR3, version 4 generates parse tree (AST) by default. JavaLexer lexer = new JavaLexer(input); CommonTokenStream tokens = new CommonTokenStream(lexer); JavaParser parser = new JavaParser(tokens); ParserRuleContext<Token> tree = parser.compilationUnit(); // parse   ParseTreeWalker walker = new ParseTreeWalker(); // create standard walker MyListener extractor = new MyListener(parser); walker.walk(extractor, tree); // initiate walk of tree with listener Check https://theantlrguy.atlassian.net/wiki/display/ANTLR4/Parse+Tree+Listeners. Also, see https://github.com/antlrjavaparser/antlr-java-parser (ANTLR4 Java code parser). Hope this helps :)