title: Scala Map and ConcurrentHashMap throw a java.lang.UnsupportedOperationException
body: <p>With this simple code</p>
  
  <pre><code>import scala.collection.JavaConversions._
  new java.util.concurrent.ConcurrentHashMap[String,String]  ().toMap.put("abc","def")
  </code></pre>
  
  <p>Scala throw a java.lang.UnsupportedOperationException.</p>
  
  <p>Why ?</p>