Can java have Protected or Private Constructor

Question

Hi,
can java have Priavte or protected constructor,
as we know java have default and public constructor ,
and in using singleton design patters we can use private & protected constructor,
so, what is the main logic,
Regards,
Prabhat

Answer 1

Hi,
Yes, We can declare constructor as private/public/protected also.
Having only private constructors means that you can't instantiate the class from outside the class (although instances could still be created from within the class - more about this later). However, when you instantiate a class, you must first initialize all superclasses of that class by invoking their constructors. If one of the superclasses has only private constructors declared, we have a problem. We can't invoke the superclass' constructor which means that we can't instantiate our object. Because of this, we've essentially made a class that can't be extended.
example:
class TheWorld
private static TheWorld _instance = null;
private TheWorld() {}
public static TheWorld instance()
if ( _instance == null )
_instance = new TheWorld();
return _instance;
public void spin() {...}
public class WorldUser
public static void main(String[] args)
TheWorld.instance().spin();
}