public String runMain(String className, String[] args, String stdin) {

        Class<?> target;
        try {
            target = ByteClassLoader.publicFindClass(className);
        } catch (ClassNotFoundException e) {
            return "Internal error: main class "+className+" not found";
        }

        Method main;
        try {
            main = target.getMethod("main", new Class[]{String[].class});
        } catch (NoSuchMethodException e) { 
            return "Class "+className+" needs public static void main(String[] args)";
        }

        if (stdin != null)
            try {
                System.setIn(new java.io.ByteArrayInputStream(stdin.getBytes("UTF-8")));
            }
            catch (SecurityException | java.io.UnsupportedEncodingException e) {
                return "Internal error: can't setIn";
            }

        int modifiers = main.getModifiers();
        if (modifiers != (Modifier.PUBLIC | Modifier.STATIC))
            return "Class "+className+" needs public static void main(String[] args)";
        try {
            // first is null since it is a static method
            main.invoke(null, new Object[]{args});
            return null;
        }
        catch (IllegalAccessException e) {
            return "Internal error invoking main";
        }
        catch (InvocationTargetException e) {
            if (e.getTargetException() instanceof RuntimeException)
                throw (RuntimeException)(e.getTargetException());

            
            java.io.StringWriter sw = new java.io.StringWriter();
            java.io.PrintWriter pw = new java.io.PrintWriter(sw);
            e.getTargetException().printStackTrace(pw);

            return "Internal error handling error " + e.getTargetException() + sw.toString();

            //if (e.getTargetException() instanceof Error)
            //  throw (Error)(e.getTargetException());
            
        }
    }