Java : parse java source code, extract methods

I wish to parse java source code files, and extract the methods source code.

I would need a method like this :

/** Returns a map with key = method name ; value = method source code */
Map<String,String> getMethods(File javaFile);

Is there a simple way to achieve this, a library to help me build my method, etc. ?

Download the java parser from https://javaparser.org/

You'll have to write some code. This code will invoke the parser... it will return you a CompilationUnit:

            InputStream in = null;
            CompilationUnit cu = null;
            try
            {
                    in = new SEDInputStream(filename);
                    cu = JavaParser.parse(in);
            }
            catch(ParseException x)
            {
                 // handle parse exceptions here.
            }
            finally
            {
                  in.close();
            }
            return cu;

Note: SEDInputStream is a subclass of input stream. You can use a FileInputStream if you want.

You'll have to create a visitor. Your visitor will be easy because you're only interested in methods:

  public class MethodVisitor extends VoidVisitorAdapter
  {
        public void visit(MethodDeclaration n, Object arg)
        {
             // extract method information here.
             // put in to hashmap
        }
  }

To invoke the visitor, do this:

  MethodVisitor visitor = new MethodVisitor();
  visitor.visit(cu, null);

QDOX is a more lightweight parser, that does only parse down to the method level, i.e. the method body is not being parsed into statements. It gives you more or less, what you ask for, even though the you would have navigate the model to find the right name, as it doesn't index classes and methods by name.

You can build your parser with one of parser generators:

1. ANTLR
2. JavaCC
3. SableCC

Also, you can use (or study how it works) something ready-made. There are Java Tree Builder which uses JavaCC and RefactorIt which uses ANTLR.