This means that the Standard Java null
values in Json Object causes them to be ignored and do-not appear in the output. This is baiscally done to compact the output. Where as the sentinel JSONObject.NULL
will add null in the output string.
An example will make you clear
JSONObject jObject = new JSONObject();
jObject.put("First Name", null);
jObject.put("Last Name", JSONObject.NULL);
//Print jObject
Log.d("JSON OBJECT", jObject.toString());
This will give the output like
{"Last Name":null}