After seeing the example I understood that you are trying to do something similar as asked in Java JsonObject array value to key
jsonObjSend.put("elementi", new JSONArray(new Object[] { "value1", "value2", "value3"} ));
To simplify:
JSONArray arr = new JSONArray();
arr.put("value1");
arr.put("value2");
//...
jsonObjSend.put("elementi", arr);