What's the access modifier of the default constructor in java?

Question

We all know that if we don\'t specifically define a constructor, the compiler inserts an invisible zero-parameter constructor. I thought its access modifier was public, but

Answer 1

I thought its access modifier is public, but when I deal with a inner class issue, I found maybe I was wrong.

Yup. Indeed, I found myself in the same situation a couple of years ago. I was surprised by an error (through Guice injection, which made it slightly harder to find).

The key is to check the spec, in this case section 8.8.9:

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.

So in this case, your constructor is implicitly protected.

Answer 2

I would like to point out one more thing that I recently got. If you define a default constructor for your class then it's acess specifier will be what you assign. For example,

 public class A{
       A(){
       // do some stuff
       }
    }

Here the access specifier of the default constructor is package access and not public access (that of the class). However

 public class A{
       // no constructor is defined
    }

Here the compiler will sympathize with you and give you a default constructor whose access specifier will be same as the class , that is public.

Answer 3

In addition to what Jon pretty well stated, here is an image example, for the visual guys.

If there is no constructor in a class, compiler automatically creates a default constructor.

Here is an example that successfully depicts the above rule:

For further reference, please refer here.