Cannot invoke a method, even if it's public

here's my code. And it throws

can not access a member of class sun.management.ClassLoadingImpl with modifiers "public"

I first reflect the method, then call it. And as you see, getObjectName is a public method, but why cannot I invoke it?

import java.lang.management.ManagementFactory;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Hello world!
 */
public class App {
    public static void main(String[] args) throws InvocationTargetException, IllegalAccessException {
        Method[] methods = ManagementFactory.class.getMethods();
        System.out.println(ManagementFactory.getClassLoadingMXBean().getObjectName());
        for (Method method : methods) {
            if (method.getName().startsWith("get") && method.getName().endsWith("Bean")) {
                System.out.println(method.getName());
                Object bean = method.invoke(null);
                printBean(bean);
            }
        }
    }

    private static void printBean(Object bean) throws InvocationTargetException, IllegalAccessException {
        Method[] methods = bean.getClass().getMethods();
        for (Method method : methods) {
            if (method.getName().startsWith("get")) {
                System.out.println(method.getName());
                System.out.println(method.getName() + ":" + method.invoke(bean).toString());
            }
        }
    }
}