title: How to create optional parameters for own annotations?
body: <p>Following is the annotation code</p>
  
  <pre><code>public @interface ColumnName {
     String value();
     String datatype();
   }
  </code></pre>
  
  <p>I would like to make <code>datatype</code> an optional parameter, for example</p>
  
  <pre><code>@ColumnName(value="password") 
  </code></pre>
  
  <p>should be a valid code.</p>