private constructors

[Vidya Krishnamurthi]

Hi all
I had a confusion regarding private constructors.
Supposing i define a class Test whose constructor is made private is it legal to instantiate a class like this
Test t = new Test();
shouldn't this give a compile error.
thanks

[Anupam Sinha]

Hi Vidya
Anything declared as private is accessible only to that class. Going by this definition you can use the constructor of this class in the class itself but not outside the class. Hence your code would work if it is inside the class where the private constructor is.

[Ashish Hareet]

Hi Vidya,
It is legal to instantiate a class having a private constructor as it's only constructor.
The catch is where you can instantiate the class. You can instantiate such a class in the class itself & nowhere else.
So,

Test t = new Test();

is fine if it is somewhere in the Test class itself & it will result in a compiler error if it is outside the Test class.
HTH
Ashish Hareet

[Vidya Krishnamurthi]

yeah i got the point thanks a lot

[carlos olmos]

This private constructors are usefull when your creating a Singleton class: this way only the class itself may create the instance and make sure there is only one.
regards.
Carlos Olmos.

[Thomas Paul]

An inner class can have a private constructor which could still be used by the enclosing class.

public class InnerPrivate {
    private class Inner {
        private Inner() {}
        private String m() {return "m";}
    }
    
    public static void main(String[] args) {
        System.out.println(new InnerPrivate().new Inner().m());
    }    
}