What is the explicit constructor access modifier?

Question

Suppose there is a class A. Which of the following two access modifiers is a default one for a constructor?

public A()
{
    private A()
    {
         //some code....
    }

    protected A()
    {
         //some code....
    }
}

http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html — Brian Roach, Jan 06 '13 at 03:23
If you understand what the access modifiers mean there is no question here, and if you don't you should look them up in the JLS. Not a real question. — user207421, Jan 06 '13 at 21:52

score 6 · Answer 1 · edited May 23 '17 at 12:27

It means the exact same thing as modifiers to functions and variables, only now it refers to who can CONSTRUCT an instance of the class.

public - any one can call the constructor from anywhere in the code.

private - Unable to construct from outside the class - typically used to enable control over who gets to instanciate the class with the use of a static member factory method. A good example of an appication found here

protected - Like private but now inheritance is involved - any subclass factory method can be used because now they can call this constructor.

As @dasblinkenlight mentions, if you do not specify any modifier, then they default to being package-private, meaning they are only visible to classes within the package.

For the sake of completeness, you may want to mention the `A() {}` with its *default access* for use by members of the same package. — Sergey Kalinichenko, Jan 06 '13 at 03:14

What is the explicit constructor access modifier?

1 Answers1