title: how to send data from an activity to interface
body: <p>i have an activity . which gets me a user id . and i want to get it into an interface,(seems like a stupid question to me too)</p>
  
  <p>for eg. 
  code snippet. (to show what i want to get done)</p>
  
  <p><strong>ACTIVITY</strong></p>
  
  <pre><code>class MainActivity extends Activity{
  
           public static string user;
           public void onCreate(Bundle savedInstanceState)
           {
                  super.onCreate(savedInstanceState);
                  user="1";  //I WANT TO SEND THIS VALUE TO MY INTERFACE SHOWN BELOW
           }
  }     
  </code></pre>
  
  <p><strong>INTERFACE</strong></p>
  
  <pre><code>package random.test.done;
  
  import retrofit2.Call;
  import retrofit2.http.GET;
  
  public interface RequestExample{
  
      @GET("claim.php?id=1" + MainActivity.user); /// how to get that user data here ? 
      Call&lt;JSONResponseClaim&gt; getJSONClaim();
  }
  </code></pre>
  
  <p>@GET("claim.php?id=1" + MainActivity.user); // this line in the interface gives error when hover over MainActivity.user (Attribute value must be constant)</p>
  
  <p><strong>questions are in the comments in the above code snippets</strong></p>