Object  nullObj = null; 

private static void JSONObject() {

// TODO Auto-generated method stub

JSONObject wangxiaoer = new JSONObject();

wangxiaoer.put("name", "王小二");

wangxiaoer.put("age", 25.2);

wangxiaoer.put("birthday", "1990-01-01");

wangxiaoer.put("major" ,new String[]{"炒菜","挖掘机"});

wangxiaoer.put("car",nullObj);

wangxiaoer.put("house",nullObj);

System.out.println(wangxiaoer.toString());

}

}

得出来的结果是这样的

{"car":null,"birthday":"1990-01-01","age":25.2,"name":"王小二","house":null,"major":[Ljava.lang.String;@b166b5}