如何从.java文件中获取方法列表

Question

I have a path of a .java file in my Java program. I want to get the list of methods that are available in the .java file.

For example, I have a .java file at 'C:\\temp\\Foo.java' as follows:

class Foo{
    public int add(int a, int b){ return a+b;}
    public int sub(int a, int b){ return a-b;}
}

In my program, I want to get the method names add and sub . Is there any java api to achieve the same? I know that for .class file, we can achieve it using Reflection, but is it possible for .java file?

Answer 1

You can use javaparser library.

Here is sample code from their wiki page:

public class MethodPrinter {

    public static void main(String[] args) throws Exception {
        // creates an input stream for the file to be parsed
        FileInputStream in = new FileInputStream("test.java");

        CompilationUnit cu;
        try {
            // parse the file
            cu = JavaParser.parse(in);
        } finally {
            in.close();
        }

        // visit and print the methods names
        new MethodVisitor().visit(cu, null);
    }

    /**
     * Simple visitor implementation for visiting MethodDeclaration nodes. 
     */
    private static class MethodVisitor extends VoidVisitorAdapter {

        @Override
        public void visit(MethodDeclaration n, Object arg) {
            // here you can access the attributes of the method.
            // this method will be called for all methods in this 
            // CompilationUnit, including inner class methods
            System.out.println(n.getName());
        }
    }
}