I got this demo code from school and it is supposed to show me a parse tree. After I generate the parser and test the rule in that class, I'm supposed to run the Java class, but I don't seem the get a parser tree. Does anyone know what I'm doing wrong?
And the code from the Java file
MyAntlrDemo
import java.io.IOException;
import org.antlr.v4.runtime.*;
import org.antlr.v4.runtime.tree.ParseTree;
/**
* Antlr Java Parser Demo: read a Java file and print methods found by visiting the parse tree.
* Don't forget to generate ANTLR Java parser class files first!
*/
public class MyAntlrDemo extends Java8ParserBaseVisitor<Void> {
/**
* Main Method
*/
public static void main(String[] args) throws IOException {
//String file = "./src/MyAntlrDemo.java"; // input this source file
String file = "./exampleJava.txt"; // a shorter Java example input
CharStream chars = CharStreams.fromFileName(file);
Java8Lexer lexer = new Java8Lexer(chars);
CommonTokenStream tokens = new CommonTokenStream(lexer); // lexer converts text to tokens
Java8Parser parser = new Java8Parser(tokens);
ParseTree tree = parser.compilationUnit(); // create tree from staring rule: compilationunit
System.out.println("Number of syntax errors found: " + parser.getNumberOfSyntaxErrors());
// walk the tree and do something with it
MyAntlrDemo visitor = new MyAntlrDemo(); // extends JavaBaseVisitor<Void>
System.out.println("STARTING VISIT");
visitor.visit(tree); // calls visitCompilationUnit and other overridden methods below
}
@Override
public Void visitCompilationUnit(Java8Parser.CompilationUnitContext ctx) {
System.out.println("Inside visitCompilationUnit");
return visitChildren(ctx);
}
@Override
public Void visitMethodDeclaration(Java8Parser.MethodDeclarationContext ctx) {
System.out.println("found method:" + ctx.getText());
System.out.println("Methodname: " + ctx.methodHeader().methodDeclarator().Identifier().getText());
return super.visitMethodDeclaration(ctx);
}
}
Also the .txt file
ExampleJava.txt
class Jan {
private int foo; // comment
public Jan() { }
public int eenMethode(){
return foo * 2;
}
}
The output message:
ANTLR preview:
