// 14.1 In terms of inheritance, what is the point of declaring the constructor as private?

 // Answer:

 //    1. private member cannot be inherited, thus the class cannot be inherited.

 //    2. constructor is private, so you cannot new an object freely. Only through public static member method can you get an instance of this class.

 //    3. with this you can implement Singleton Pattern, which ensures that a class has at most one instance within an application. You can but you don't have to do it.

 public class TestJava {

     private static TestJava instance = null;

     public static TestJava getInstance() {

         if (instance == null) {

             instance = new TestJava();

         }

         return instance;

     }

     public void f() {

         System.out.println("TestJava::f()");

     }

     private TestJava() {

     }

     public static void main(String[] args) {

         System.out.println("Hello world.");

         TestJava testJava = TestJava.getInstance();

         testJava.f();

     }

 }