title: Problem using generic map with wildcard
body: <p>I have a method that returns a <code>map</code> defined as:</p>
  
  <pre><code>public Map&lt;String, ?&gt; getData();
  </code></pre>
  
  <p>The actual implementation of this method is not clear to me, but, when I try to do:</p>
  
  <pre><code>obj.getData().put("key","value")
  </code></pre>
  
  <p>I get following compile time error message:</p>
  
  <blockquote>
    <p>The method put(String, capture#9-of ?)
    in the type Map
    is not applicable for the arguments
    (String, String)</p>
  </blockquote>
  
  <p>What is the problem? Is <code>String</code> not of type anything?</p>
  
  <p>Thanks in advance.</p>