以下是代码：

String str="{\"code\":\"na7ne\",\"identity\":1671760031645,\"password\":\"88888888\",\"username\":\"fuj\"}";
JSONObject jsonObject = JSON.parseObject(str);
System.out.println(str);
for(Map.Entry<String,Object> map: jsonObject.entrySet()){
    if(map.getKey().contains("password"))
        JSONPath.set(jsonObject,"$."+map.getKey(),"***");
}
System.out.println(jsonObject.toJSONString());

以下是输出内容:

{"code":"na7ne","identity":1671760031645,"password":"88888888","username":"fuj"}
{"password":"***","code":"na7ne","identity":1671760031645,"username":"fuj"}