java - 在java中创建动态树

Question

我需要创建一个基于JSON的动态树数据。我有一个类别列表，每个类别都有一个子类别，其中有一个子类别有一个子类别。

我的JSON数据示例为:

    [
      {
        "Id": 110,
        "Name": "Winter Collection",
        "ParentCategoryId": 0,
        "Description": null,
        "DisplayOrder": 0
      },
      {
        "Id": 111,
        "Name": "Hoodies",
        "ParentCategoryId": 110,
        "Description": null,
        "DisplayOrder": 0
      },
      {
        "Id": 113,
        "Name": "Pullover/Sweater",
        "ParentCategoryId": 110,
        "Description": null,
        "DisplayOrder": 0
      }
{
    "Id": 116,
    "Name": "Jacket \u0026 Blazer",
    "ParentCategoryId": 110,
    "Description": null,
    "DisplayOrder": 0
  },
  {
    "Id": 118,
    "Name": "Sweatshirts",
    "ParentCategoryId": 110,
    "Description": null,
    "DisplayOrder": 0
  },
  {
    "Id": 119,
    "Name": "Winter Accessories",
    "ParentCategoryId": 110,
    "Description": null,
    "DisplayOrder": 2
  },
  {
    "Id": 23,
    "Name": "Men\u0027s T-Shirt",
    "ParentCategoryId": 0,
    "Description": null,
    "DisplayOrder": 1
  },
  {
    "Id": 24,
    "Name": "Men\u0027s T-Shirt (Full sleeve)",
    "ParentCategoryId": 23,
    "Description": null,
    "DisplayOrder": -1
  },
  {
    "Id": 79,
    "Name": "Black T-Shirt",
    "ParentCategoryId": 23,
    "Description": null,
    "DisplayOrder": 0
  },
  {
    "Id": 80,
    "Name": "White T-Shirt",
    "ParentCategoryId": 23,
    "Description": null,
    "DisplayOrder": 0
  },
  {
    "Id": 81,
    "Name": "Red T-Shirt",
    "ParentCategoryId": 23,
    "Description": null,
    "DisplayOrder": 0
  },
  {
    "Id": 82,
    "Name": "Blue T-Shirt",
    "ParentCategoryId": 23,
    "Description": null,
    "DisplayOrder": 0
  },
    ...............
    ] 

主要Categories谁的parentid==0和Subcategories ( child )是谁的parentId等于 id的Categories 。随后每Subcategory可容纳Child 。

我需要建一棵树。如果JSON数据返回List<Category>那么最终的树将是这个类 List (即 List<ParentCategory> )

public class ParentCategory {
   Category category;
   List<ParentCategory> Subcategories;
}

如何在 Java 中表示这棵树数据结构？

Answer 1

最简单的方法是通过两次遍历列表:

第 1 步:创建 Map<Integer, ParentCategory>由 id 键控的类别，忽略 ParentCategoryId 和子类别。

Pass2:使用 ParentCategoryId 查找在 Pass1 中创建的 ParentCategory 并将其添加到其子类别