title: Private constructor in abstract class
body: <p>In Java what is the purpose of using private constructor in an abstract class? </p>
  
  <p>In a review I got this question, and I am curious, for what situation we need to use the constructor in such way?</p>
  
  <p>I think it can be used in pair with another constructor in abstract class, but this is very trivial. Also it can be used for constructing static inner classes which will excend abstract class.</p>
  
  <p>Maybe there is more elegant usage?</p>