try{ HashMap<String , Object> outer = new HashMap<String , Object>(); HashMap<String , String> inner = new HashMap<String , String>(); inner.put("AAA", "BBB"); outer.put("aaa", inner); outer.put("bbb" , null); outer.put("ccc" , ""); JSONObject json = new JSONObject(outer); Log.d("TEST" , json.toStri…</string></string></string></string>