title: Java GSON: Getting the list of all keys under a JSONObject
body: <p>I have got GSON as a JSON parser in Java, but the keys aren't always the same.<br>
  For example. I have the following JSON:  </p>
  
  <blockquote>
    <p>{ "The Object I already know": {<br>
        "key1":"value1",<br>
        "key2":"value2",<br>
        "AnotherObject": { "anotherKey1":"anotherValue1", "anotherKey2":"anotherValue2" }<br>
    }</p>
  </blockquote>
  
  <p>I have already got the JSONObject "The Object I already know". Now I need to get all of the JSONElements for this Object, this would be "Key1", "Key2" and "AnotherObject".<br>
  Thanks in advance.<br>
  EDIT: The Output should be a String Array with all the keys for the JSONObject</p>