What is the access modifier of an anonymous class's constructor?

Question

NOTE: This is a self-answered question. It may be a very simple one but I thought it would be worth sharing.

Suppose I have an anonymous class declaration:

MyObject myObj1 = new MyObject() {

};

where MyObject is:

class MyObject {

    public MyObject() { // explicit public constructor
    }

    ...
}

From this section of the Java Language Specification (emphasis mine):

An anonymous class cannot have an explicitly declared constructor. Instead, an anonymous constructor is implicitly declared for an anonymous class.

If I try to get the number of public constructors:

// Number of public constructors; prints 0
System.out.println(myObj1.getClass().getConstructors().length);

it prints zero as expected, i.e. the anonymous constructor is not public.

It is also not private, since if we call the following from a different class in the same package where the anonymous class is defined (by passing around the instance myObj1):

myObj1.getClass().getDeclaredConstructor().newInstance();

it completes without an IllegalAccessException.

What is the access modifier of the implicit constructor in an anonymous class?

Answer 1

The anonymous constructor acts similar to the default constructor that the compiler also creates for a normal class that does not declare constructors. In this case:

In a class type, if the class is declared public, then the default constructor is implicitly given the access modifier public (§6.6); if the class is declared protected, then the default constructor is implicitly given the access modifier protected (§6.6); if the class is declared private, then the default constructor is implicitly given the access modifier private (§6.6); otherwise, the default constructor has the default access implied by no access modifier.

In other words, the anonymous constructor is only accessible in the same package as the anonymous class.