java递归生成树

1.获取数据

public List<TreeClassifyRespVO> getTreeClassifyList(ClassifyPageReqVO reqVO) {
    List<ClassifyDO> classifyList = classifyMapper.selectList(reqVO);
    List<TreeClassifyRespVO> childClassifyResp = ClassifyConvert.INSTANCE.convertList01(classifyList);
    return getClassifyTree(childClassifyResp);
}

2.生成树形结构

public List<TreeClassifyRespVO> getClassifyTree(List<TreeClassifyRespVO> childClassifyResp) {
    // 返回的树形数据
    List<TreeClassifyRespVO> tree = new ArrayList<TreeClassifyRespVO>();
    // 第一次遍历
    for (TreeClassifyRespVO treeClassify : childClassifyResp) {
        // 找到根节点，这里我的根节点的pid为0
        if (treeClassify.getPid()==0) {
            tree.add(findChild(treeClassify, childClassifyResp));
        }
    }
    return tree;
}

3.查询子节点

private TreeClassifyRespVO findChild(TreeClassifyRespVO treeClassify, List<TreeClassifyRespVO> list) {
    // 定义list用于存储子节点
    List<TreeClassifyRespVO> children = new ArrayList<TreeClassifyRespVO>();
    for (TreeClassifyRespVO node : list) {
        // 找到根节点，这里我的根节点的pid为0
        if (node.getPid().equals(treeClassify.getId())) {
            // 调用递归
            children.add(findChild(node, list));
        }
    }
    treeClassify.setChildren(children);
    return treeClassify;
}

4.效果