java

 1 @UtilityClass
 2 public class TreeUtil {
 3     /**
 4      * 两层循环实现建树
 5      *
 6      * @param treeNodes 传入的树节点列表
 7      * @return
 8      */
 9     public <T extends TreeNode> List<T> bulid(List<T> treeNodes, Object root) {
10 
11         List<T> trees = new ArrayList<>();
12 
13         for (T treeNode : treeNodes) {
14 
15             if (root.equals(treeNode.getParentId())) {
16                 trees.add(treeNode);
17             }
18 
19             for (T it : treeNodes) {
20                 if (it.getParentId() == treeNode.getId()) {
21                     if (treeNode.getChildren() == null) {
22                         treeNode.setChildren(new ArrayList<>());
23                     }
24                     treeNode.add(it);
25                 }
26             }
27         }
28         return trees;
29     }
30 
31     /**
32      * 使用递归方法建树
33      *
34      * @param treeNodes
35      * @return
36      */
37     public <T extends TreeNode> List<T> buildByRecursive(List<T> treeNodes, Object root) {
38         List<T> trees = new ArrayList<T>();
39         for (T treeNode : treeNodes) {
40             if (root.equals(treeNode.getParentId())) {
41                 trees.add(findChildren(treeNode, treeNodes));
42             }
43         }
44         return trees;
45     }
46 
47     /**
48      * 递归查找子节点
49      *
50      * @param treeNodes
51      * @return
52      */
53     public <T extends TreeNode> T findChildren(T treeNode, List<T> treeNodes) {
54         for (T it : treeNodes) {
55             if (treeNode.getId() == it.getParentId()) {
56                 if (treeNode.getChildren() == null) {
57                     treeNode.setChildren(new ArrayList<>());
58                 }
59                 treeNode.add(findChildren(it, treeNodes));
60             }
61         }
62         return treeNode;
63     }
64 }

 1 @Data
 2 public class TreeNode {
 3     protected int id;
 4     protected int parentId;
 5     protected String name;
 6     protected List<TreeNode> children = new ArrayList<TreeNode>();
 7 
 8     public void add(TreeNode node) {
 9         children.add(node);
10     }
11 }

1 @Data
2 @EqualsAndHashCode(callSuper = true)
3 public class DeptTree extends TreeNode {
4     private String name;
5 }

 1 public List<DeptTree> getDeptTree(List<SysDept> depts) {
 2         List<DeptTree> treeList = depts.stream()
 3                 .filter(dept -> !dept.getDeptId().equals(dept.getParentId()))
 4                 .map(dept -> {
 5                     DeptTree node = new DeptTree();
 6                     node.setId(dept.getDeptId());
 7                     node.setParentId(dept.getParentId());
 8                     node.setName(dept.getName());
 9                     return node;
10                 }).collect(Collectors.toList());
11         return TreeUtil.bulid(treeList, 0);
12     }