java多叉树的实现类，完成树的初始化和遍历

在java编程中，经常会用到创建树形结构的菜单或者目录结构，这就需要设计一个树形类，帮助实现类似功能。本文从其他地方摘抄了一个多叉树类设计，包括两个文件（TreeNode.java和TreeHelper.java） TreeNode类完成树节点的数据结构，TreeHelper类通过输入一个TreeNode列表，生成一颗有一个树根的树！希望能有帮助。

一：树节点的定义（TreeNode.java） 

package com.tree;import java.util.List;import java.util.ArrayList;import java.io.Serializable;public class TreeNode implements Serializable {    private int parentId;    private int selfId;    protected String nodeName;    protected Object obj;    protected TreeNode parentNode;    protected List<TreeNode> childList;    public TreeNode() {        initChildList();    }    public TreeNode(TreeNode parentNode) {        this.getParentNode();        initChildList();    }    public boolean isLeaf() {        if (childList == null) {            return true;        } else {            if (childList.isEmpty()) {                return true;            } else {                return false;            }        }    }    /* 插入一个child节点到当前节点中 */    public void addChildNode(TreeNode treeNode) {        initChildList();        childList.add(treeNode);    }    public void initChildList() {        if (childList == null)            childList = new ArrayList<TreeNode>();    }    public boolean isValidTree() {        return true;    }    /* 返回当前节点的父辈节点集合 */    public List<TreeNode> getElders() {        List<TreeNode> elderList = new ArrayList<TreeNode>();        TreeNode parentNode = this.getParentNode();        if (parentNode == null) {            return elderList;        } else {            elderList.add(parentNode);            elderList.addAll(parentNode.getElders());            return elderList;        }    }    /* 返回当前节点的晚辈集合 */    public List<TreeNode> getJuniors() {        List<TreeNode> juniorList = new ArrayList<TreeNode>();        List<TreeNode> childList = this.getChildList();        if (childList == null) {            return juniorList;        } else {            int childNumber = childList.size();            for (int i = 0; i < childNumber; i++) {                TreeNode junior = childList.get(i);                juniorList.add(junior);                juniorList.addAll(junior.getJuniors());            }            return juniorList;        }    }    /* 返回当前节点的孩子集合 */    public List<TreeNode> getChildList() {        return childList;    }    /* 删除节点和它下面的晚辈 */    public void deleteNode() {        TreeNode parentNode = this.getParentNode();        int id = this.getSelfId();        if (parentNode != null) {            parentNode.deleteChildNode(id);        }    }    /* 删除当前节点的某个子节点 */    public void deleteChildNode(int childId) {        List<TreeNode> childList = this.getChildList();        int childNumber = childList.size();        for (int i = 0; i < childNumber; i++) {            TreeNode child = childList.get(i);            if (child.getSelfId() == childId) {                childList.remove(i);                return;            }        }    }    /* 动态的插入一个新的节点到当前树中 */    public boolean insertJuniorNode(TreeNode treeNode) {        int juniorParentId = treeNode.getParentId();        if (this.parentId == juniorParentId) {            addChildNode(treeNode);            return true;        } else {            List<TreeNode> childList = this.getChildList();            int childNumber = childList.size();            boolean insertFlag;            for (int i = 0; i < childNumber; i++) {                TreeNode childNode = childList.get(i);                insertFlag = childNode.insertJuniorNode(treeNode);                if (insertFlag == true)                    return true;            }            return false;        }    }    /* 找到一颗树中某个节点 */    public TreeNode findTreeNodeById(int id) {        if (this.selfId == id)            return this;        if (childList.isEmpty() || childList == null) {            return null;        } else {            int childNumber = childList.size();            for (int i = 0; i < childNumber; i++) {                TreeNode child = childList.get(i);                TreeNode resultNode = child.findTreeNodeById(id);                if (resultNode != null) {                    return resultNode;                }            }            return null;        }    }    /* 遍历一棵树，层次遍历 */    public void traverse() {        if (selfId < 0)            return;        print(this.selfId);        if (childList == null || childList.isEmpty())            return;        int childNumber = childList.size();        for (int i = 0; i < childNumber; i++) {            TreeNode child = childList.get(i);            child.traverse();        }    }    public void print(String content) {        System.out.println(content);    }    public void print(int content) {        System.out.println(String.valueOf(content));    }    public void setChildList(List<TreeNode> childList) {        this.childList = childList;    }    public int getParentId() {        return parentId;    }    public void setParentId(int parentId) {        this.parentId = parentId;    }    public int getSelfId() {        return selfId;    }    public void setSelfId(int selfId) {        this.selfId = selfId;    }    public TreeNode getParentNode() {        return parentNode;    }    public void setParentNode(TreeNode parentNode) {        this.parentNode = parentNode;    }    public String getNodeName() {        return nodeName;    }    public void setNodeName(String nodeName) {        this.nodeName = nodeName;    }    public Object getObj() {        return obj;    }    public void setObj(Object obj) {        this.obj = obj;    }}

二：TreeHelper.java 

package com.tree;import java.util.List;import java.util.Iterator;import java.util.ArrayList;import java.util.HashMap;public class TreeHelper {    private TreeNode root;    private List<TreeNode> tempNodeList;    private boolean isValidTree = true;    public TreeHelper() {    }    public TreeHelper(List<TreeNode> treeNodeList) {        tempNodeList = treeNodeList;        generateTree();    }    public static TreeNode getTreeNodeById(TreeNode tree, int id) {        if (tree == null)            return null;        TreeNode treeNode = tree.findTreeNodeById(id);        return treeNode;    }    /** generate a tree from the given treeNode or entity list */    public void generateTree() {        HashMap nodeMap = putNodesIntoMap();        putChildIntoParent(nodeMap);    }    /**     * put all the treeNodes into a hash table by its id as the key     *      * @return hashmap that contains the treenodes     */    protected HashMap putNodesIntoMap() {        int maxId = Integer.MAX_VALUE;        HashMap nodeMap = new HashMap<String, TreeNode>();        Iterator it = tempNodeList.iterator();        while (it.hasNext()) {            TreeNode treeNode = (TreeNode) it.next();            int id = treeNode.getSelfId();            if (id < maxId) {                maxId = id;                this.root = treeNode;            }            String keyId = String.valueOf(id);            nodeMap.put(keyId, treeNode);            // System.out.println("keyId: " +keyId);        }        return nodeMap;    }    /**     * set the parent nodes point to the child nodes     *      * @param nodeMap     *            a hashmap that contains all the treenodes by its id as the key     */    protected void putChildIntoParent(HashMap nodeMap) {        Iterator it = nodeMap.values().iterator();        while (it.hasNext()) {            TreeNode treeNode = (TreeNode) it.next();            int parentId = treeNode.getParentId();            String parentKeyId = String.valueOf(parentId);            if (nodeMap.containsKey(parentKeyId)) {                TreeNode parentNode = (TreeNode) nodeMap.get(parentKeyId);                if (parentNode == null) {                    this.isValidTree = false;                    return;                } else {                    parentNode.addChildNode(treeNode);                    // System.out.println("childId: " +treeNode.getSelfId()+" parentId: "+parentNode.getSelfId());                }            }        }    }    /** initialize the tempNodeList property */    protected void initTempNodeList() {        if (this.tempNodeList == null) {            this.tempNodeList = new ArrayList<TreeNode>();        }    }    /** add a tree node to the tempNodeList */    public void addTreeNode(TreeNode treeNode) {        initTempNodeList();        this.tempNodeList.add(treeNode);    }    /**     * insert a tree node to the tree generated already     *      * @return show the insert operation is ok or not     */    public boolean insertTreeNode(TreeNode treeNode) {        boolean insertFlag = root.insertJuniorNode(treeNode);        return insertFlag;    }    /**     * adapt the entities to the corresponding treeNode     *      * @param entityList     *            list that contains the entities     *@return the list containg the corresponding treeNodes of the entities     */    public static List<TreeNode> changeEnititiesToTreeNodes(List entityList) {        OrganizationEntity orgEntity = new OrganizationEntity();        List<TreeNode> tempNodeList = new ArrayList<TreeNode>();        TreeNode treeNode;        Iterator it = entityList.iterator();        while (it.hasNext()) {            orgEntity = (OrganizationEntity) it.next();            treeNode = new TreeNode();            treeNode.setObj(orgEntity);            treeNode.setParentId(orgEntity.getParentId());            treeNode.setSelfId(orgEntity.getOrgId());            treeNode.setNodeName(orgEntity.getOrgName());            tempNodeList.add(treeNode);        }        return tempNodeList;    }    public boolean isValidTree() {        return this.isValidTree;    }    public TreeNode getRoot() {        return root;    }    public void setRoot(TreeNode root) {        this.root = root;    }    public List<TreeNode> getTempNodeList() {        return tempNodeList;    }    public void setTempNodeList(List<TreeNode> tempNodeList) {        this.tempNodeList = tempNodeList;    }}