Need help to understand constructor marked private?

[rizwana mujawar]

They say "Constructor can use any modifier including private. A private constructor means only code within the same class itself can instantiate an object of that type,so if private constructor class wants to allow instance of the class to be used,the class must provide a static method or a variable that allows access an instance created from within the class ".
I dint get the above statement.. Can anyone help me to understand this statement. Please...!
Thanks

[John Jai]

A private constructor means only code within the same class itself can instantiate an object of that type

Sample -

public class PrivateConstructorSample {
	public static void main(String...args){
		A a = new A(); // Compiler error here.
	}
}

class A {
	private A() {
		System.out.println("In class A private constructor");
	}
}

the class must provide a static method or a variable that allows access an instance created from within the class

Sample -

public class GetPrivateInstance {
	public static void main(String...args){
		// Method 1 - get instance of B by calling a static method
		B b = B.getInstanceOfB();
		b.print();
		
		// Method 2 
		B bb = B.bb;
		bb.print();
	}
}

class B {
	private static B b = new B();
	
	public static B bb = new B();
	
	private B() {
		System.out.println("In constructor B");
	}
	
	public void print(){
		System.out.println("hello!");
	}
	public static B getInstanceOfB() {
		return b;
	}
}

[Md. Minhajur Rahman]

"A private constructor means only code within the same class itself can instantiate an object of that type,so if private constructor class wants to allow instance of the class to be used, the class must provide a static method or a variable that allows access an instance created from within the class ". because static method or variable is the only way as only static members are accessible before creating any instance of any class. As constructor is private, so you can't create an instance of that class at outside of the class, so can't access any instance method. So Static member is the way if private constructor class wants to allow instance of the class to be used.