org.json.JSONObject orgJSON = new org.json.JSONObject();
// The method put(String, Collection) is ambiguous for the type JSONObject
//orgJSON.put("null", null);
net.sf.json.JSONObject netJSON = new net.sf.json.JSONObject();
netJSON.put("null", null);

System.out.println("netJSON" + netJSON); // 控制臺輸出 : netJSON{}