添加具有多个Arrylist的类对象

Question

嗨，我正在尝试使用arrylists添加类对象，并需要以json格式显示它。我将gson库用于json格式，而iam tring将java对象绑定到jsonformat中，如下所示

" {"type": "record","name": "Doc","doc": "adoc","fields": [{"name": "id","type": "string"}, {"name": "user_friends_count","type": ["int", "null"]}]"

这些下面的类和主要方法

public class RootFields {
public String type;
public String name;
public String doc;

}

public class Fields {
public String name;
public String type;

}

这是我的主要方法

public class JavaToJson{


    public static void main(String[] args) {
        // TODO Auto-generated method stub      
RootFields root = new RootFields();
List<Fields> F2 = new ArrayList<Fields>();
Fields F1 = new Fields();
Fields Fields1 = new Fields();
Fields Fields2 = new Fields();
root.type = "record";
root.name = "Doc";
root.doc = "adoc";
F1.name = "id";
F1.type = "string";
Fields1.name = "user_friends_count";
Fields1.type = "int";
Fields2.name = "user_location";
Fields2.type = "int";
GsonBuilder builder = new GsonBuilder();
Gson gson = builder.create();

root.F2.add(F1);
System.out.println(gson.toJson(root));

    }

}

它显示了我无法解决编译错误F2或不是 F2中“ root.F2.add（F1）”中的字段的地方，我在哪里出错，请提前帮忙。

Answer 1

您尚未在RootFields F2声明为字段。 尽管据我了解，您应该使用List或数组，而不是每个Fields实例使用多个Fields 。

Answer 2

class RootFields {
    public String type;
    public String name;
    public String doc;
    List <Fields> filelds = new ArrayList<>();
}