public JSONArray names() {
        JSONArray ja = new JSONArray();
        Iterator<String> keys = this.keys();
        while (keys.hasNext()) {
            ja.put(keys.next());
        }
        return ja.length() == 0 ? null : ja;
    }
@author Robert HG (254963746@qq.com) on 12/28/15.
lts-core/src/main/java/com/github/ltsopensource/json/JSONObject.java