Java 从嵌套的POJO形成Json

我将POJO嵌套如下。所有的POJO都在同一个包中。请看学生的名字是pojo，所有其他pojo都在里面

 class Student{

     String firstName;
     String lastName;

     List <Activities> activites;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public List<Activities> getActivites() {
        return activites;
    }

    public void setActivites(List<Activities> activites) {
        this.activites = activites;
    }

    }

    class Activites{

    List<Quipments> quipments;

    String time;

    public List<Quipments> getQuipments() {
        return quipments;
    }

    public void setQuipments(List<Quipments> quipments) {
        this.quipments = quipments;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }



    }

    class Quipments{

    String Type;

    public String getType() {
        return Type;
    }

    public void setType(String type) {
        Type = type;
    }

    }

想用下面这样的东西吗

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.JSONValue;

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请建议使用此非常流行的库：

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对于必需的库，请参阅json simple，它似乎太简单了：-我认为您将需要大量的工作来重新设计使用它的轮子。为什么不试试flexjson、gson或jackson呢？

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.JSONValue;

String sample = "{firstName: \"mardar\", lastName: \"pandit\"}";
com.google.gson.Gson gson = new com.google.gson.Gson();
Student student = gson.fromJson(sample, Student.class);
System.out.println(gson.toJson(student));