对一个JSONArray数据，按照两个字段分级重新组成新的JSONArray

假设你有一个 JSONArray 数据如下：

[
  {
    "name": "John",
    "age": 30,
    "department": "IT"
  },
  {
    "name": "Mary",
    "age": 25,
    "department": "Sales"
  },
  {
    "name": "Peter",
    "age": 35,
    "department": "IT"
  }
]

现在你想要将这个 JSON 数组按照部门和年龄进行分组，重新组成一个新的 JSON 数组。你可以使用 Java 语言中的 JSONObject 和 JSONArray 类来完成这个任务，实现代码如下：

import org.json.*;

public class Main {
  public static void main(String[] args) {
    JSONArray jsonArray = new JSONArray("[{\"name\":\"John\",\"age\":30,\"department\":\"IT\"},{\"name\":\"Mary\",\"age\":25,\"department\":\"Sales\"},{\"name\":\"Peter\",\"age\":35,\"department\":\"IT\"}]");
    JSONArray newJsonArray = new JSONArray();

    for (int i = 0; i < jsonArray.length(); i++) {
      JSONObject jsonObject = jsonArray.getJSONObject(i);
      String department = jsonObject.getString("department");
      int age = jsonObject.getInt("age");

      // Find the index of the existing department object in the newJsonArray
      int index = -1;
      for (int j = 0; j < newJsonArray.length(); j++) {
        JSONObject existingDepartmentObject = newJsonArray.getJSONObject(j);
        if (existingDepartmentObject.getString("name").equals(department)) {
          index = j;
          break;
        }
      }

      // If the department object doesn't exist, create one
      if (index == -1) {
        JSONObject newDepartmentObject = new JSONObject();
        newDepartmentObject.put("name", department);
        JSONArray newAgeArray = new JSONArray();
        newAgeArray.put(age);
        newDepartmentObject.put("ages", newAgeArray);
        newJsonArray.put(newDepartmentObject);
      } else {
        // If the department object already exists, add the age to the existing array
        JSONObject existingDepartmentObject = newJsonArray.getJSONObject(index);
        JSONArray existingAgeArray = existingDepartmentObject.getJSONArray("ages");
        existingAgeArray.put(age);
      }
    }

    System.out.println(newJsonArray.toString());
  }
}

运行上面的代码，你会得到一个新的 JSON 数组：

[
  {
    "name": "IT",
    "ages": [30, 35]
  },
  {
    "name": "Sales",
    "ages": [25]
  }
]

新的 JSON 数组按照部门分组，每个部门下面有一个年龄数组，包含该部门员工的年龄。