title: Why does compilation take longer in Play 2.3.4 (activator) vs Play 2.2.4 (play)?
body: <p><strong>Scenario 1:</strong></p>
  
  <p>Start Play <strong>2.2.4</strong> project with command <code>play ~run</code>, then move some code from A.java to B.java => the following output:</p>
  
  <p><code>[info] Compiling 2 Java sources to D:\MyProject\target\scala-2.10\classes...
  [info] Compiling 1 Java source to D:\MyProject\target\scala-2.10\classes...
  [warn] Note: D:\MyProject\app\controllers\AdminController.java uses or overrides a deprec
  ated API.
  [warn] Note: Recompile with -Xlint:deprecation for details.
  [success] Compiled in 4s</code></p>
  
  <p><strong>Scenario 2:</strong></p>
  
  <p>Start Play <strong>2.3.4</strong> (activator) project with command <code>activator ~run</code>, then move some code from A.java to B.java => the following output:</p>
  
  <p><code>[info] Compiling 9 Scala sources and 368 Java sources to D:\MyProject\target\scala-2.11\c
  lasses...
  [warn] Note: Some input files use or override a deprecated API.
  [warn] Note: Recompile with -Xlint:deprecation for details.
  [success] Compiled in 64s</code></p>
  
  <p>Why does Play 2.3.4 recompile all the sources in the second case? Is there a setting for that? Both scenarios are for the same project and in both cases I ran <code>play/activator clean</code> and <code>play/activator compile</code> before making the change.</p>