title: Int vs Integer: type mismatch, found: Int, required: String
body: <p>I type these to the scala interpreter:</p>
  
  <pre><code>val a : Integer = 1;
  val b : Integer = a + 1;
  </code></pre>
  
  <p>And I get the message:</p>
  
  <pre><code>&lt;console&gt;:5: error: type mismatch;
   found   : Int(1)
   required: String
         val b : Integer = a +1
                              ^
  </code></pre>
  
  <p>Why? How can I solve this?
  This time I need Integers due to Java interoperability reasons.</p>