java构建树形结构

实体

@Data
public class SysCategoryTree {
    private static final long serialVersionUID = 1L;

    private String id;

    /** 父级节点 */
    private String pid;

    /** 类型名称 */
    private String name;

    /** 类型编码 */
    private String code;


    @TableField(exist = false)
    private List<SysCategoryTree> nodes;

    public SysCategoryTree() {
        // 默认使用哈希表
        nodes = new ArrayList<>();
    }
}

构建树形结构

  public static List<SysCategoryTree> buildSysCategoryTree(List<SysCategoryTree> node) {
        List<SysCategoryTree> res = new ArrayList<>();
        Map<String, SysCategoryTree> map = new HashMap<>();
        node.forEach(n -> map.put(n.getId(), n));
        node.forEach(n -> {
            //表示不是根目录
            if (n.getPid() != null) {
                if (n.getPid().equals("0")) {
                    res.add(n);
                } else {
                    //get当前父级节点
                    SysCategoryTree tree = map.get(n.getPid());
                    //根据父节点未查询到上级，代表错误数据，删除
                    if (tree != null) {
                        //将当前对象添加到当前父级节点的子级节点属性中
                        tree.getNodes().add(n);
                    }
                }
            }
        });
        return res;
    }

根据节点id获取该节点下所有数据

public List<SysCategoryTree> getNodeTree(List<SysCategoryTree> resList,String pid){
		List<SysCategoryTree> sysCategoryTree = new ArrayList<>();
		for (int i = 0; i < resList.size(); i++) {
			String id = resList.get(i).getId();
			List<SysCategoryTree> nodes = resList.get(i).getNodes();
			if(id.equals(pid)){
				sysCategoryTree.add(resList.get(i));
			}
		}
		if(CollectionUtils.isEmpty(sysCategoryTree)){
			for (SysCategoryTree sysCategoryTree1:resList){
				if(CollectionUtils.isNotEmpty(sysCategoryTree1.getNodes())){
						if(CollectionUtils.isNotEmpty(getNodeTree(sysCategoryTree1.getNodes(),pid))){
							return getNodeTree(sysCategoryTree1.getNodes(),pid);
						}else{
							getNodeTree(sysCategoryTree1.getNodes(),pid);
						}
				}
			}
		}

		return sysCategoryTree;
	}