Java中id,pid格式數(shù)據(jù)轉(zhuǎn)樹(shù)和森林結(jié)構(gòu)工具類實(shí)現(xiàn)

更新時(shí)間：2023年05月24日 10:52:38 作者：小熊vip

本文主要介紹了Java中id,pid格式數(shù)據(jù)轉(zhuǎn)樹(shù)和森林結(jié)構(gòu)工具類實(shí)現(xiàn)，文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

樹(shù)形結(jié)構(gòu)很多地方都有應(yīng)用，比如我們?cè)跇?gòu)造網(wǎng)站后臺(tái)的授權(quán)限樹(shù)的時(shí)候，再比如我們?cè)谠O(shè)計(jì)多級(jí)留言的時(shí)候、還有分類等等。

有些時(shí)候我們的樹(shù)形結(jié)構(gòu)并不需要過(guò)多設(shè)計(jì)，這是因?yàn)槲覀兊暮芏鄷r(shí)候?qū)@棵樹(shù)的要求不高（兩層、三層就行了），這時(shí)候我們很容易的會(huì)按照層級(jí)劃分樹(shù)形結(jié)構(gòu)，然后查詢數(shù)據(jù)庫(kù)的時(shí)候會(huì)一層一層的嵌套查詢。如果層次比較淺這種做法是可取的（或者我們本來(lái)就不打算一次將樹(shù)加載完全，而是在需要時(shí)再加載，那分層級(jí)的多次加載也許有用武之地）。但是考慮這種情況：我們的樹(shù)比較深，而且要一次加載完全。要是按照一層一層的加載原則，那么光是訪問(wèn)數(shù)據(jù)庫(kù)的查詢語(yǔ)句就是指數(shù)形式的了。性能肯定不好。那么除了一層一層的查詢好有更好的辦法嗎？肯定是有的，多查詢一些資料會(huì)發(fā)現(xiàn)這種做法比較常見(jiàn)了：（id，pid），通俗說(shuō)就是一個(gè)節(jié)點(diǎn)只需要記住自己的id和父親的id（根節(jié)點(diǎn)沒(méi)有pid可以設(shè)置一個(gè)特殊值）就可以擁有呈現(xiàn)這棵樹(shù)的完整結(jié)構(gòu)全部信息了，仔細(xì)想一想自己學(xué)過(guò)的數(shù)據(jù)結(jié)構(gòu)，是不是這樣的？好了這樣一來(lái)我們?cè)谠O(shè)計(jì)數(shù)據(jù)庫(kù)的時(shí)候就可以很輕松的設(shè)計(jì)一棵樹(shù)的樹(shù)形結(jié)構(gòu)了。那么有個(gè)問(wèn)題，我們?cè)谡宫F(xiàn)出來(lái)的時(shí)候總不能直接顯示一連串的（id，pid）集合吧。我們要的是樹(shù)形結(jié)構(gòu)。這時(shí)候我們其實(shí)非常想實(shí)現(xiàn)的是從（id，pid）到

（id，children【】）的轉(zhuǎn)化。畢竟我們?cè)谡宫F(xiàn)樹(shù)形結(jié)構(gòu)的時(shí)候后一種格式更適合頁(yè)面的呈現(xiàn)，而前一種比較適合數(shù)據(jù)的存儲(chǔ)格式。

好了廢話不多說(shuō)了，下面是代碼示例：

首先是自定義節(jié)點(diǎn)類：

/**
 * 節(jié)點(diǎn)類
 * @author bearsmall
 *
 */
public class TreeNode {
    private int id;//主鍵ID
    private int pid;//父節(jié)點(diǎn)ID
    private Object content;//節(jié)點(diǎn)內(nèi)容
    private List<TreeNode> children = new ArrayList<TreeNode>();//子孫節(jié)點(diǎn)
    public TreeNode(int id, Object content) {
        this.id = id;
        this.content = content;
    }
    public TreeNode(int id, int pid, Object content) {
        this.id = id;
        this.pid = pid;
        this.content = content;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getPid() {
        return pid;
    }
    public void setPid(int pid) {
        this.pid = pid;
    }
    public Object getContent() {
        return content;
    }
    public void setContent(Object content) {
        this.content = content;
    }
    public List<TreeNode> getChildren() {
        return children;
    }
    public void setChildren(List<TreeNode> children) {
        this.children = children;
    }
    @Override
    public String toString() {
        return "TreeNode [id=" + id + ", pid=" + pid + ", content=" + content
                + ", children=" + children + "]";
    }
}

然后是樹(shù)節(jié)點(diǎn)管理類：

/**
 * 樹(shù)節(jié)點(diǎn)管理類
 * 
 * @author bearsmall
 *
 */
public class TreeNodeManager {
    private List<TreeNode> list;// 樹(shù)的所有節(jié)點(diǎn)
    public TreeNodeManager(TreeNode[] items) {
        list = new ArrayList<TreeNode>();
        for (TreeNode treeNode : items) {
            list.add(treeNode);
        }
    }
    public TreeNodeManager(List<TreeNode> items) {
        list = items;
    }
    /**
     * 根據(jù)節(jié)點(diǎn)ID獲取一個(gè)節(jié)點(diǎn)
     * 
     * @param id
     *            節(jié)點(diǎn)ID
     * @return 對(duì)應(yīng)的節(jié)點(diǎn)對(duì)象
     */
    public TreeNode getTreeNodeAT(int id) {
        for (TreeNode treeNode : list) {
            if (treeNode.getId() == id)
                return treeNode;
        }
        return null;
    }
    /**
     * 獲取樹(shù)的根節(jié)點(diǎn)
     * 
     * @return 一棵樹(shù)的根節(jié)點(diǎn)
     */
    public TreeNode getRoot() {
        for (TreeNode treeNode : list) {
            if (treeNode.getPid() == 0)
                return treeNode;
        }
        return null;
    }
}

最后是樹(shù)節(jié)點(diǎn)轉(zhuǎn)化類：

/**
 * 節(jié)點(diǎn)歸并類
 * @author bearsmall
 *
 */
public class TreeNodeMerger {
    /**
     * 將節(jié)點(diǎn)數(shù)組歸并為一棵樹(shù)（填充節(jié)點(diǎn)的children域）
     * 時(shí)間復(fù)雜度為O(n^2)
     * @param items 節(jié)點(diǎn)域
     * @return
     */
    public static TreeNode merge(TreeNode[] items){
        TreeNodeManager treeNodeManager = new TreeNodeManager(items);
        for (TreeNode treeNode : items) {
            if(treeNode.getPid()!=0){
                TreeNode t = treeNodeManager.getTreeNodeAT(treeNode.getPid());
                t.getChildren().add(treeNode);
            }
        }
        return treeNodeManager.getRoot();
    }
    /**
     * 將節(jié)點(diǎn)數(shù)組歸并為一棵樹(shù)（填充節(jié)點(diǎn)的children域）
     *  時(shí)間復(fù)雜度為O(n^2)
     * @param items 節(jié)點(diǎn)域
     * @return
     */
    public static TreeNode merge(List<TreeNode> items){
        TreeNodeManager treeNodeManager = new TreeNodeManager(items);
        for (TreeNode treeNode : items) {
            if(treeNode.getPid()!=0){
                TreeNode t = treeNodeManager.getTreeNodeAT(treeNode.getPid());
                t.getChildren().add(treeNode);
            }
        }
        return treeNodeManager.getRoot();
    }
}

簡(jiǎn)單測(cè)試一下：

public class Main {
    public static void main(String[] args) {
        TreeNode[] treeNodes = new TreeNode[10];
        treeNodes[0] = new TreeNode(1, 0, "");
        treeNodes[1] = new TreeNode(2, 1, "");
        treeNodes[2] = new TreeNode(3, 1, "");
        treeNodes[3] = new TreeNode(4, 2, "");
        treeNodes[4] = new TreeNode(5, 3, "");
        treeNodes[5] = new TreeNode(6, 4, "");
        treeNodes[6] = new TreeNode(7, 3, "");
        treeNodes[7] = new TreeNode(8, 5, "");
        treeNodes[8] = new TreeNode(9, 6, "");
        treeNodes[9] = new TreeNode(10, 9, "");
        TreeNode treeNode = TreeNodeMerger.merge(treeNodes);
        JSONArray jsonArray = JSONArray.fromObject(treeNode);
        System.out.println(jsonArray);
    }
}

輸出結(jié)果：

[{
        "children" : [{
                "children" : [{
                        "children" : [{
                                "children" : [{
                                        "children" : [{
                                                "children" : [],
                                                "pid" : 9,
                                                "id" : 10,
                                                "content" : ""
                                            }
                                        ],
                                        "pid" : 6,
                                        "id" : 9,
                                        "content" : ""
                                    }
                                ],
                                "pid" : 4,
                                "id" : 6,
                                "content" : ""
                            }
                        ],
                        "pid" : 2,
                        "id" : 4,
                        "content" : ""
                    }
                ],
                "pid" : 1,
                "id" : 2,
                "content" : ""
            }, {
                "children" : [{
                        "children" : [{
                                "children" : [],
                                "pid" : 5,
                                "id" : 8,
                                "content" : ""
                            }
                        ],
                        "pid" : 3,
                        "id" : 5,
                        "content" : ""
                    }, {
                        "children" : [],
                        "pid" : 3,
                        "id" : 7,
                        "content" : ""
                    }
                ],
                "pid" : 1,
                "id" : 3,
                "content" : ""
            }
        ],
        "pid" : 0,
        "id" : 1,
        "content" : ""
    }
]

這種格式是不是更清晰呢？

森林管理類：

/**
 * 森林節(jié)點(diǎn)管理類
 * 
 * @author bearsmall
 *
 */
public class ForestNodeManager {
    private List<TreeNode> list;// 森林的所有節(jié)點(diǎn)
    public ForestNodeManager(TreeNode[] items) {
        list = new ArrayList<TreeNode>();
        for (TreeNode treeNode : items) {
            list.add(treeNode);
        }
    }
    public ForestNodeManager(List<TreeNode> items) {
        list = items;
    }
    /**
     * 根據(jù)節(jié)點(diǎn)ID獲取一個(gè)節(jié)點(diǎn)
     * 
     * @param id
     *            節(jié)點(diǎn)ID
     * @return 對(duì)應(yīng)的節(jié)點(diǎn)對(duì)象
     */
    public TreeNode getTreeNodeAT(int id) {
        for (TreeNode treeNode : list) {
            if (treeNode.getId() == id)
                return treeNode;
        }
        return null;
    }
    /**
     * 獲取樹(shù)的根節(jié)點(diǎn)【一個(gè)森林對(duì)應(yīng)多顆樹(shù)】
     * 
     * @return 樹(shù)的根節(jié)點(diǎn)集合
     */
    public List<TreeNode> getRoot() {
        List<TreeNode> roots = new ArrayList<TreeNode>();
        for (TreeNode treeNode : list) {
            if (treeNode.getPid() == 0)
                roots.add(treeNode);
        }
        return roots;
    }
}

森林節(jié)點(diǎn)歸并類：

/**
 * 節(jié)點(diǎn)歸并類
 * @author bearsmall
 *
 */
public class ForestNodeMerger {
    /**
     * 將節(jié)點(diǎn)數(shù)組歸并為一個(gè)森林（多棵樹(shù)）（填充節(jié)點(diǎn)的children域）
     * 時(shí)間復(fù)雜度為O(n^2)
     * @param items 節(jié)點(diǎn)域
     * @return 多棵樹(shù)的根節(jié)點(diǎn)集合
     */
    public static List<TreeNode> merge(TreeNode[] items){
        ForestNodeManager forestNodeManager = new ForestNodeManager(items);
        for (TreeNode treeNode : items) {
            if(treeNode.getPid()!=0){
                TreeNode t = forestNodeManager.getTreeNodeAT(treeNode.getPid());
                t.getChildren().add(treeNode);
            }
        }
        return forestNodeManager.getRoot();
    }
    /**
     * 將節(jié)點(diǎn)數(shù)組歸并為一個(gè)森林（多棵樹(shù)）（填充節(jié)點(diǎn)的children域）
     * 時(shí)間復(fù)雜度為O(n^2)
     * @param items 節(jié)點(diǎn)域
     * @return 多棵樹(shù)的根節(jié)點(diǎn)集合
     */
    public static List<TreeNode> merge(List<TreeNode> items){
        ForestNodeManager forestNodeManager = new ForestNodeManager(items);
        for (TreeNode treeNode : items) {
            if(treeNode.getPid()!=0){
                TreeNode t = forestNodeManager.getTreeNodeAT(treeNode.getPid());
                t.getChildren().add(treeNode);
            }
        }
        return forestNodeManager.getRoot();
    }
}

測(cè)一下：

public class Main2 {
    public static void main(String[] args) {
        TreeNode[] treeNodes = new TreeNode[10];
        treeNodes[0] = new TreeNode(1, 0, "");
        treeNodes[1] = new TreeNode(2, 0, "");
        treeNodes[2] = new TreeNode(3, 1, "");
        treeNodes[3] = new TreeNode(4, 2, "");
        treeNodes[4] = new TreeNode(5, 3, "");
        treeNodes[5] = new TreeNode(6, 4, "");
        treeNodes[6] = new TreeNode(7, 3, "");
        treeNodes[7] = new TreeNode(8, 5, "");
        treeNodes[8] = new TreeNode(9, 6, "");
        treeNodes[9] = new TreeNode(10, 9, "");
        List<TreeNode> tns = ForestNodeMerger.merge(treeNodes);
        JSONArray jsonArray = JSONArray.fromObject(tns);
        System.out.println(jsonArray);
    }
}

打印輸出：

[{
        "children" : [{
                "children" : [{
                        "children" : [{
                                "children" : [],
                                "pid" : 5,
                                "id" : 8,
                                "content" : ""
                            }
                        ],
                        "pid" : 3,
                        "id" : 5,
                        "content" : ""
                    }, {
                        "children" : [],
                        "pid" : 3,
                        "id" : 7,
                        "content" : ""
                    }
                ],
                "pid" : 1,
                "id" : 3,
                "content" : ""
            }
        ],
        "pid" : 0,
        "id" : 1,
        "content" : ""
    }, {
        "children" : [{
                "children" : [{
                        "children" : [{
                                "children" : [{
                                        "children" : [],
                                        "pid" : 9,
                                        "id" : 10,
                                        "content" : ""
                                    }
                                ],
                                "pid" : 6,
                                "id" : 9,
                                "content" : ""
                            }
                        ],
                        "pid" : 4,
                        "id" : 6,
                        "content" : ""
                    }
                ],
                "pid" : 2,
                "id" : 4,
                "content" : ""
            }
        ],
        "pid" : 0,
        "id" : 2,
        "content" : ""
    }
]

到此這篇關(guān)于Java中id,pid格式數(shù)據(jù)轉(zhuǎn)樹(shù)和森林結(jié)構(gòu)工具類實(shí)現(xiàn)的文章就介紹到這了,更多相關(guān)Java id,pid格式數(shù)據(jù)轉(zhuǎn)樹(shù)內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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