The use of private constructor is to serve singleton classes. A singleton class is one which limits the number of objects creation to one. By providing a private constructor you prevent class instances from being created in any place other than this very class..
Consequently, what is private constructor?
A private constructor is a special instance constructor. It is generally used in classes that contain static members only. If a class has one or more private constructors and no public constructors, other classes (except nested classes) cannot create instances of this class.
Secondly, what is constructor Java? Constructor is a block of code that initializes the newly created object. A constructor resembles an instance method in java but it's not a method as it doesn't have a return type. Constructor has same name as the class and looks like this in a java code.
In this way, is it possible to have a private constructor in Java?
Yes. Class can have private constructor. Even abstract class can have private constructor. By making constructor private, we prevent the class from being instantiated as well as subclassing of that class.
Should constructors be public or private?
No, Constructors can be public , private , protected or default (no access modifier at all). Making something private doesn't mean nobody can access it. It just means that nobody outside the class can access it. So private constructor is useful too.
Related Question Answers
What is the difference between static and private constructor?
Static Constructor is called automatically before the first instance of the class or any static data is referenced. It is called only once for any number of classes instance is created. Private constructor is a special constructor that generally used in class that contains only static members.Can a constructor be final?
No, a constructor can't be made final. A final method cannot be overridden by any subclasses. In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors. Therefore, java does not allow final keyword before a constructor.Can constructor be static?
constructor is implicitly called to initialize an object, so there is no purpose in having a static constructor. Java does not permit to declare a constructor as static. A constructor always belongs to some object. If a constructor is static, an object of subclass cannot access.What happens if I make a constructor private?
By providing a private constructor you prevent class instances from being created in any place other than this very class. There are several use cases for providing such constructor. Your class instances are created in a static method. The static method is then declared as public .Can constructor be protected?
protected constructor can be accessed from its own class, its subclasses, all other classes belonging to the same package and subclasses of other packages. public constructor can be accessible from anywhere. EJB3 specification says the entities should have either a no-argument protected or private constructor.Can we override private methods?
No, a private method cannot be overridden since it is not visible from any other class. You have declared a new method for your subclass that has no relation to the superclass method. One way to look at it is to ask yourself whether it would be legal to write super.Can constructor be inherited?
Constructors are not members of classes and only members are inherited. You cannot inherit a constructor. That is, you cannot create a instance of a subclass using a constructor of one of it's superclasses.What is true constructor?
What is true about constructor? Explanation: Constructor returns a new object with variables defined as in the class. Instance variables are newly created and only one copy of static variables are created. Explanation: No instance can be created of abstract class.Can abstract class have private constructor?
A private constructor in an abstract class can also serve the purpose of sealed classes (like in Scala or Kotlin etc.). Since you can still provide subclasses from within the abstract class, but outsiders cannot extend/implement (as @Marko Topolnik answered).Can constructor return a value?
Constructors cannot return a value; they return the constructed object, so to speak. You get an error because the compiler is looking for a constructor that takes a string as its argument. A class contains constructors that are invoked to create objects from the class blueprint.What is Polymorphism in Java?
Polymorphism in Java is a concept by which we can perform a single action in different ways. We can perform polymorphism in java by method overloading and method overriding. If you overload a static method in Java, it is the example of compile time polymorphism. Here, we will focus on runtime polymorphism in java.Can we use this () and super () in a method?
this() and super(), both are the constructors that's why must be the first statement. But we can use both in a program. this(): It is used to call, same class Default or Parametrized Constructor. super(): It is used to call, immediate super/parent class Default or Parametrized Constructor.What is static in Java?
In Java, a static member is a member of a class that isn't associated with an instance of a class. Instead, the member belongs to the class itself. As a result, you can access the static member without first creating a class instance. The value of a static field is the same across all instances of the class.What is singleton class in Java?
Singleton Class in Java. In object-oriented programming, a singleton class is a class that can have only one object (an instance of the class) at a time. To design a singleton class: Make constructor as private. Write a static method that has return type object of this singleton class.Can we override static method?
Static methods cannot be overridden because they are not dispatched on the object instance at runtime. The compiler decides which method gets called. Static methods can be overloaded (meaning that you can have the same method name for several methods as long as they have different parameter types).Can we override constructor in Java?
Constructor Overriding is never possible in Java. This is because, Constructor looks like a method but name should be as class name and no return value. Overriding means what we have declared in Super class, that exactly we have to declare in Sub class it is called Overriding.How do you make a constructor private?
First, initiate a constructor as private. Then create a private static instance of this singleton class. Keep in mind to NOT instantiate it. Then, write a static method, which checks the static instance member for null and initiates the instance.How many types of constructors are there in Java?
two types
What is constructor and its types?
A constructor is a special type of function with no return type. We define a method inside the class and constructor is also defined inside a class. A constructor is called automatically when we create an object of a class. We can't call a constructor explicitly. Let us see the types of constructor. 
