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Can we declare a constructor as private in Java?
Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.
Conditions for Private Constructor
- A private constructor does not allow a class to be subclassed.
- A private constructor does not allow to create an object outside the class.
- If all the constant methods are there in our class we can use a private constructor.
- If all the methods are static then we can use a private constructor.
- If we try to extend a class which is having private constructor compile time error will occur.
Example
class SingletonObject {
private SingletonObject() {
System.out.println("In a private constructor");
}
public static SingletonObject getObject() {
// we can call this constructor
if (ref == null)
ref = new SingletonObject();
return ref;
}
private static SingletonObject ref;
}
public class PrivateConstructorDemo {
public static void main(String args[]) {
SingletonObject sObj = SingletonObject.getObject();
}
}Output
In a private constructor
Updated on: 30-Jul-2019
9K+ Views
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