树形数据

@Data
public class Tree  {
    private Integer id;
    private String name;
    private Integer age;
    private String sex;
    private Integer parentId;
    private List<Tree> children;
    public String getId() {
        if (this.id == null) {
            return null;
        } else {
            return this.id;
        }
    }
    public String getParentId() {
        if (this.parentId == null) {
            return null;
        } else {
            return this.parentId;
        }
    }
    public void setChildTreeList(List<Tree> treeList) {
        this.children = treeList;
    }
}

@Data
public class TreeBuildFactory<T> {
    //顶级节点的父节点id(默认-1)
    private Integer rootParentId = -1;
    
    public TreeBuildFactory() {}
    
    public TreeBuildFactory(Integer rootParentId) {
        this.rootParentId = rootParentId;
    }
    //传过来一个List集合
    public List<T> treeBuild(List<T> treeList) {
        //将每个节点的构造一个子树
        for (T tree : treeList) {
            this.buildChildTreeList(treeList, tree, new ArrayList<>());
        }

        //只保留上级是根节点的节点，也就是只留下所有一级节点
        ArrayList<T> results = new ArrayList<>();
        for (T tree : treeList) {
            if (tree.getParentId().equals(rootParentId)) {
                results.add(tree);
            }
        }
        return results;
    }
    
    //获取树形集合的主要循环体
    private void buildChildTreeList(List<T> treeList, T tree, List<T> list) {
        if (treeList == null || tree == null) {
            return;
        }
        //获取下一级的集合
        List<T> childTreeList = getChildTreeList(treeList, tree);
        
        if (childTreeList.size() > 0) {
            for (T childTreeListItem : childTreeList) {
                buildChildTreeList(treeList, childTreeListItem, new ArrayList<>());
            }
        }

        list.addAll(childTreeList);
        tree.setChildTreeList(list);
    }
    
    //获取下一级的集合
    private List<T> getChildTreeList(List<T> treeList, T tree) {
        List<T> childTreeList = new ArrayList<>();
        for (T treeListItem : treeList) {
            if (treeListItem.getParentId().equals(tree.getId())) {
                childTreeList.add(treeListItem);
            }
        }
        return childTreeList;
    }

}