首先，可以使用Online JSON Viewer工具清晰地查看JSON的具体结构。
https://www.bejson.com/jsonviewernew/

让我们拿这段JSON文本来举例子吧：

{"code":"200","updateTime":"2021-08-06T02:17+08:00","fxLink":"http://hfx.link/2ax1","now":{"obsTime":"2021-08-06T02:12+08:00","temp":"23","feelsLike":"24","icon":"101","text":"多云","wind360":"135","windDir":"东南风","windScale":"2","windSpeed":"8","humidity":"79","precip":"0.0","pressure":"1001","vis":"19","cloud":"91","dew":"21"},"refer":{"sources":["Weather China"],"license":["no commercial use"]}}

格式化后：

{
  "code": "200",
  "updateTime": "2021-08-06T02:17+08:00",
  "fxLink": "http://hfx.link/2ax1",
  "now": {
    "obsTime": "2021-08-06T02:12+08:00",
    "temp": "23",
    "feelsLike": "24",
    "icon": "101",
    "text": "多云",
    "wind360": "135",
    "windDir": "东南风",
    "windScale": "2",
    "windSpeed": "8",
    "humidity": "79",
    "precip": "0.0",
    "pressure": "1001",
    "vis": "19",
    "cloud": "91",
    "dew": "21"
  },
  "refer": {
    "sources": [
      "Weather China"
    ],
    "license": [
      "no commercial use"
    ]
  }
}

在 Online Json Viewer 中的视图如下：

重要总结：

前面图标为 { } 的项所对应的 Class 为: JSONObject
前面图标为 [ ] 的项所对应的 Class 为: JSONArray
前面图标为方块的项所对应的 Class中的方法为: JSONObject.getT() 或 JSONArray.getT()

Java 示例：

下面的代码用来获取 license.0 对应的文本(String)值

//主类代码省略
String json = "JSON文本, 此处略";
JSONObject obj = JSON.parseObject(json);
JSONObject obj_refer = obj.getJSONObject("refer");   //refer
JSONArray arr_license = obj_refer.getJSONArray("license");   //refer.license
String str_license = arr_license.getString(0); //refer.license.0
System.out.println(str_license);

示例输出:

no commercial use

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【Java】 FastJson 库的实际使用 (1)

重要总结：

Java 示例：