java实现tree树形结构

树节点遍历工具类:

@UtilityClass
public class TreeUtil {
    /**
     * 两层循环实现建树
     *
     * @param treeNodes 传入的树节点列表
     * @return
     */
    public <T extends TreeNode> List<T> bulid(List<T> treeNodes, Object root) {

        List<T> trees = new ArrayList<>();

        for (T treeNode : treeNodes) {

            if (root.equals(treeNode.getParentId())) {
                trees.add(treeNode);
            }

            for (T it : treeNodes) {
                if (it.getParentId() == treeNode.getId()) {
                    if (treeNode.getChildren() == null) {
                        treeNode.setChildren(new ArrayList<>());
                    }
                    treeNode.add(it);
                }
            }
        }
        return trees;
    }

    /**
     * 使用递归方法建树
     *
     * @param treeNodes
     * @return
     */
    public <T extends TreeNode> List<T> buildByRecursive(List<T> treeNodes, Object root) {
        List<T> trees = new ArrayList<T>();
        for (T treeNode : treeNodes) {
            if (root.equals(treeNode.getParentId())) {
                trees.add(findChildren(treeNode, treeNodes));
            }
        }
        return trees;
    }

    /**
     * 递归查找子节点
     *
     * @param treeNodes
     * @return
     */
    public <T extends TreeNode> T findChildren(T treeNode, List<T> treeNodes) {
        for (T it : treeNodes) {
            if (treeNode.getId() == it.getParentId()) {
                if (treeNode.getChildren() == null) {
                    treeNode.setChildren(new ArrayList<>());
                }
                treeNode.add(findChildren(it, treeNodes));
            }
        }
        return treeNode;
    }
}

   树模型:

@Data
public class TreeNode {
    protected int id;
    protected int parentId;
    protected String name;
    protected List<TreeNode> children = new ArrayList<TreeNode>();

    public void add(TreeNode node) {
        children.add(node);
    }
}

　部门树:

@Data
@EqualsAndHashCode(callSuper = true)
public class DeptTree extends TreeNode {
    private String name;
}

   构建部门树方法:

public List<DeptTree> getDeptTree(List<SysDept> depts) {
        List<DeptTree> treeList = depts.stream()
                .filter(dept -> !dept.getDeptId().equals(dept.getParentId()))
                .map(dept -> {
                    DeptTree node = new DeptTree();
                    node.setId(dept.getDeptId());
                    node.setParentId(dept.getParentId());
                    node.setName(dept.getName());
                    return node;
                }).collect(Collectors.toList());
        return TreeUtil.bulid(treeList, 0);
    }