利用栈来实现权限树

权限树结构

java中提供了对应的栈结构来进行操作

    private static void pop() {
        List<String> stringList = Arrays.asList("1", "2", "3", "4");
        Stack<String> stack = new Stack<>();
        stack.addAll(stringList);
        while (!stack.isEmpty()) {
            System.out.println(stack.pop());
        }
    }

测试输出发现输出顺序是：4、3、2、1。添加顺序是1、2、3、4

那么来测试一下对应的权限树结构：

public class TreeNode {

    public TreeNode() {
    }

    public TreeNode(Integer id, Integer parentId, String name) {
        this.id = id;
        this.parentId = parentId;
        this.name = name;
    }

    private Integer id;

    private Integer parentId;

    private String name;

    private List<TreeNode> treeNodeList = new ArrayList<>();

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getParentId() {
        return parentId;
    }

    public void setParentId(Integer parentId) {
        this.parentId = parentId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<TreeNode> getTreeNodeList() {
        return treeNodeList;
    }

    public void setTreeNodeList(List<TreeNode> treeNodeList) {
        this.treeNodeList = treeNodeList;
    }

    @Override
    public String toString() {
        return "TreeNode{" +
                "id=" + id +
                ", parentId=" + parentId +
                ", name='" + name + '\'' +
                ", treeNodeList=" + treeNodeList +
                '}';
    }
}

对应的测试类：

public class TestOne {
    public static void main(String[] args) {
        List<TreeNode> treeNodeList = new ArrayList<>();
        treeNodeList.add(new TreeNode(1, 0, "根节点"));
        treeNodeList.add(new TreeNode(2, 1, "根节点的子节点1"));
        treeNodeList.add(new TreeNode(3, 1, "根节点的子节点2"));
        treeNodeList.add(new TreeNode(4, 3, "根节点的子节点2的子节点1"));
        treeNodeList.add(new TreeNode(5, 4, "根节点的子节点2的子节点的子节点"));
        treeNodeList.add(new TreeNode(6, 3, "根节点的子节点2的子节点2"));
        Map<Integer, List<TreeNode>> collect = treeNodeList.stream().collect(Collectors.groupingBy(TreeNode::getParentId));
        System.out.println(collect);
        // 获取得到根节点
        List<TreeNode> collect1 = treeNodeList.stream().filter(treeNode -> treeNode.getParentId() == 0).collect(Collectors.toList());
        Stack<TreeNode> stack = new Stack<>();
        stack.addAll(collect1);
        while (!stack.isEmpty()) {
            TreeNode pop = stack.pop();
            List<TreeNode> treeNodes = collect.get(pop.getId());
            if (treeNodes != null && treeNodes.size() > 0) {
                pop.setTreeNodeList(treeNodes);
                stack.addAll(treeNodes);
            }
        }
        System.out.println(collect1);
    }

    private static void pop() {
        List<String> stringList = Arrays.asList("1", "2", "3", "4");
        Stack<String> stack = new Stack<>();
        stack.addAll(stringList);
        while (!stack.isEmpty()) {
            System.out.println(stack.pop());
        }
    }
}

查看对应的结点可以看到对应的输出信息，形成了一棵树结构。