title: Why abstract classes necessary?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/1912475/what-is-an-abstract-class">What is an abstract class ?</a>  </p>
  </blockquote>
  
  
  
  <p>1.What is the point of creating a class that can't be instantiated?</p>
  
  <p>Most commonly to serve as a base-class or interface (some languages have a separate interface     construct, some don't) - it doesn't know the implementation (that is to be provided by the subclasses / implementing classes)</p>
  
  <p>2.Why would anybody want such a class?</p>
  
  <pre><code>For abstraction and re-use
  </code></pre>
  
  <p>3.What is the situation in which abstract classes become NECESSARY?can anyone brief it with an example?</p>