Anonymous classes, private methods, and reflection

Question

If I create an anonymous class with a private method, and try to access the method using reflection, it will throw an IllegalAccessException. However, if I call the method on the object before saving it to a variable, it works fine:

public class Z {
    public static void main(String[] args) throws Exception {

        Object obj = new Object(){private void foo(){}};            
        obj.getClass().getDeclaredMethod("foo").invoke(obj); // throws IllegalAccessException

        new Object(){private void foo(){}}.foo(); // works
    }
}

What's the reason for the difference?

Answer 1

In the first case, you're trying to access the method by reflection, and since it is a private method, the reflector class cannot invoke it, thus it throws an IllegalAccessException.

In the second case, you're accessing the method directly, and you're allowed to since because it is an anonymous inner class to Z and you're accessing it inside Z class.