title: MapStruct : Getting error of implementation is not abstract and does not override abstract method
body: <p>I am new to MapStruct and I am currently doing a POC. I can see that <code>MapStruct</code> is able to generate an implementation class from interface for a general method </p>
  
  <pre><code>Set&lt;String&gt; integerSetToStringSet(Set&lt;Integer&gt; integers);
  </code></pre>
  
  <p>but when I use the project specific classes it gives me compilation error of <code>&lt;InterfaceName&gt;impl is not abstract and does not override the abstract method &lt;customMethod&gt;.</code> </p>
  
  <p>I am using an interface with just one method. The interface is annotated with <code>@Mapper</code> but the method is simple <code>one-to-one</code> mapping with no need of <code>@Mapping</code> annotation.</p>
  
  <p>As mentioned earlier, if I put a general method all works fine but not for project specific classes.</p>
  
  <p>Can someone give me some pointers on this issue? </p>