[CC150v4] 14.1 Java Private Constructor

Question

In terms of inheritance, what is the effect of keeping a constructor private?

Solution

If the programmer does not provide a constructor for a class, the system will always provide a default, public no-argument constructor.

To disable this default constructor, simply add a private no-argument constructor to the class.

Two categories of usage:

1. Object construction is entirely forbidden
   1. class offers only static members (sometimes called utility class)
2. Object construction is private only
   1. a class needs to prevent the caller from creating objects, like Singleton