title: how to extend a class present in a jar file?
body: <p>I have a basic question on how to extend a .class present in a jar file?</p>
  
  <p>For example, I have <code>library.jar</code> file on my build path and inside this jar file there is a class <code>ClassA.class</code></p>
  
  <p>When i try to do this in eclipse </p>
  
  <pre><code>public class ClassAImpl extends ClassA{
  }
  </code></pre>
  
  <p>It shows error saying that it cannot find ClassA.</p>
  
  <p>Does it mean that i have to download the sources of the <code>library.jar</code> and add those to my project?</p>
  
  <p>Not sure if my question is clear enough?</p>