title: Issue on formatting a json structure in java
body: <p>I want to create a json like this using java:</p>
  
  <pre><code>"foo": {
           "key1": "value1",
           "key2": "value2",
           }
  </code></pre>
  
  <p><strong><em>i know how to create a key value json or a json array</em></strong> , but i don't know how to create a <code>structure</code> like this.</p>
  
  <p>any helps?</p>
  
  <p>thanks in advance.</p>