title: Put String value in gson.JsonArray
body: <p>I want to store a <code>String</code> in a <code>JsonArray</code>.
  Ex:</p>
  
  <pre><code>"virtual_hosts": [ "some_host"]
  </code></pre>
  
  <p>How should I do this, with the help of java.</p>
  
  <pre><code>JsonArray arr = new JsonArray();
  arr.add()
  </code></pre>
  
  <p>This only lets me add a <code>JsonObject</code>, but I want to store a <code>String</code>.</p>