我已经测试了给定链接上的步骤,以检查它是否有效以及一切正常：

java Run
a = 1+2
b = a^2
c = a+b*(a-1)
a+b+c
^Z
Result: 33.0

然后我编写了自己的解析java程序如下面的结构：

|_Java.g4                                                               
|_Java.tokens                                                           
|_JavaBaseVisitor.java                                                  
|_JavaLexer.java                                                        
|_JavaLexer.tokens                                                      
|_JavaParser.java                                                       
|_JavaTreeExtractorVisitor.java                                         
|_JavaVisitor.java           
|_Run.java

Run.java如下：

import org.antlr.v4.runtime.*;
import org.antlr.v4.runtime.tree.*;

public class Run {
    public static void main(String[] args) throws Exception {
        CharStream input = CharStreams.fromFileName("F:\\Projects\\Java\\Netbeans\\ASTProj\\JavaTreeExtractor\\prog.java");
        JavaLexer lexer = new JavaLexer(input);
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        JavaParser parser = new JavaParser(tokens);
        ParseTree tree = parser.getContext();

        JavaTreeExtractorVisitor calcVisitor = new JavaTreeExtractorVisitor();
        String result = calcVisitor.visit(tree);
        System.out.println("Result: " + result);
    }
}

但是在语句ParseTree tree = parser.getContext();树对象变为null.
因为我是antlr的新手,有什么建议让我检查或任何解决方案？

(如果需要更多信息,请通知我).

TG.