测试实体

    1. @Data
    2. public class Users {
    3.     private int id;
    4.     private int parentId;
    5.     // 子节点数据
    6.     private List<Users> child;
    8.     public Users() {
    9.     }
    11.     public Users(int id, int parentId) {
    12.         this.id = id;
    13.         this.parentId = parentId;
    14.     }
    16.     @Override
    17.     public String toString() {
    18.         return "Users{" +
    19.                 "id=" + id +
    20.                 ", parentId=" + parentId +
    21.                 ", child=" + child +
    22.                 '}';
    23.     }
    24. }

    实现功能的代码

    1. public class TestTree {
    3.     public static void main(String[] args) {
    4.         List<Users> list = new ArrayList<>();
    5.         extracted(list);
    6.         List<Users> results = new ArrayList<>();
    7.         // 先获取一级节点
    8.         List<Users> collect = list.stream().filter(v -> v.getParentId() == -1).collect(Collectors.toList());
    9.         for (Users users : collect) {
    10.             List<Users> childNodes = buildChildNode(users, list);
    11.             users.setChild(childNodes);
    12.             results.add(users);
    13.         }
    14.         System.out.println(results);
    15.     }
    17.     private static List<Users> buildChildNode(Users users, List<Users> list) {
    18.         List<Users> childNodes = new ArrayList<>();
    19.         int id = users.getId();
    20.         List<Users> collect = list.stream().filter(v -> v.getParentId() == id).collect(Collectors.toList());
    21.         if (collect == null || collect.size() == 0) {
    22.             return childNodes;
    23.         }
    24.         for (Users users1 : collect) {
    25.             childNodes.add(users1);
    26.             List<Users> list1 = buildChildNode(users1, list);
    27.             if (list1 != null && list1.size() > 0) {
    28.                 users1.setChild(list1);
    29.             }
    30.         }
    31.         return childNodes;
    32.     }
    35.     /**
    36.     获取测试数据
    37.     */
    38.     private static void extracted(List<Users> list) {
    39.         Users users1 = new Users(1, -1);
    40.         list.add(users1);
    41.         Users users11 = new Users(11, 1);
    42.         list.add(users11);
    43.         Users users12 = new Users(12, 1);
    44.         list.add(users12);
    45.         Users users2 = new Users(2, -1);
    46.         list.add(users2);
    47.         Users users21 = new Users(21, 2);
    48.         list.add(users21);
    49.         Users users22 = new Users(22, 2);
    50.         list.add(users22);
    51.         Users users211 = new Users(211, 21);
    52.         list.add(users211);
    53.         Users users212 = new Users(212, 21);
    54.         list.add(users212);
    55.         Users users3 = new Users(3, -1);
    56.         list.add(users3);
    57.     }
    58. }