java实现二叉树的创建和各种遍历操作

本文是关于查找二叉树的创建和各种遍历操作。
import java.lang.Thread.State;
import java.text.spi.NumberFormatProvider;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

import javax.print.attribute.standard.NumberOfDocuments;

import org.w3c.dom.NodeList;

public class MyBinTree {
private Node root;

public MyBinTree(){    this.root= null;}//java的访问权限有下面四种：public--都可访问(公有)   protected--包内和子类可访问（保护）不写(default)--包内可访问 （默认）private--类内可访问（私有）private class Node{       int data;         //default修饰符    Node lchild;    Node rchild;    public Node(int data){        this.data= data;        this.lchild=null;        this.rchild=null;    }}//创建二叉查找树：所有节点的左子树节点都比根节点小，右子树节点都比根节点大public void buildTree(Node node,int data) {    if(root==null){        root= new Node(data);        /*  if(node==null){      开始没注意写成了这样，发现每次调用buildTree时，node都是null，发现底下传入的参数其实是root            node= new Node(data);*/    }else{        if(data<node.data){  //左孩子            if(node.lchild==null){                node.lchild= new Node(data);            }else{                buildTree(node.lchild, data);            }        }else{            if(node.rchild==null){                node.rchild=new Node(data);            }else{                buildTree(node.rchild, data);            }        }    }}//递归前序遍历public  void preOrder(Node node){    if(node!=null){        System.out.print("  "+node.data);        preOrder(node.lchild);        preOrder(node.rchild);    }}//递归中序遍历public void inOrder(Node node){    if(node!=null){        inOrder(node.lchild);        System.out.print(" "+node.data);        inOrder(node.rchild);    }}//递归后序遍历public void postOrder(Node node){    if(node!=null){        postOrder(node.lchild);        postOrder(node.rchild);        System.out.print(" "+node.data);    }} //非递归前序遍历public void preOrder2(Node node){    Stack<Node> stack = new Stack<>();    while(node!=null||!stack.isEmpty()){        //先一路向左走，找到底，把找到的节点都压入栈，并sysout出来。        while(node!=null){            System.out.print(node.data+" ");            stack.push(node);            node=node.lchild;        }        if(!stack.isEmpty()){  //抛出栈顶元素            node = stack.pop();            node= node.rchild;        }      }}//非递归的中序遍历//和前序遍历的区别就是将输出放在了栈的pop之后public void inOrder2(Node node){    Stack<Node>  stack = new Stack<>();    while(node!=null||!stack.isEmpty()){        while(node!=null){            stack.push(node);            node=node.lchild;        }        if(!stack.isEmpty()){            node=stack.pop();            System.out.print(node.data+" ");            node=node.rchild;        }    }}//后续遍历的非递归实现public void postOrder2(Node node) {    Stack<Node> stack = new Stack<>();    Node curNode= node;    Node lastNode=node;    while(curNode!=null){        stack.push(curNode);        curNode=curNode.lchild;    }    while(!stack.isEmpty()){        curNode=stack.pop();        if(curNode.rchild==null||curNode.rchild==lastNode){            System.out.print(curNode.data+" ");            lastNode=curNode;        }else{             stack.push(curNode);             curNode=curNode.rchild;             while(curNode!=null){                 stack.push(curNode);                 curNode=curNode.lchild;             }        }    }}//层次遍历public void levelTravel(Node node) {    Queue<Node> queue = new LinkedList<>();    queue.offer(node);    while(!queue.isEmpty()){        node=queue.poll();        System.out.print(node.data+" ");        if(node.lchild!=null){            queue.offer(node.lchild);        }        if(node.rchild!=null){            queue.offer(node.rchild);        }    }}public static void main(String[] args) {    int[] a = {2,4,12,45,21,6,111};      MyBinTree myBinTree= new MyBinTree();    for(int i=0;i<a.length;i++){        myBinTree.buildTree(myBinTree.root, a[i]);    }    myBinTree.preOrder(myBinTree.root);    System.out.println();    myBinTree.preOrder2(myBinTree.root);    System.out.println();    myBinTree.inOrder(myBinTree.root);    System.out.println();    myBinTree.inOrder2(myBinTree.root);    System.out.println();    myBinTree.postOrder(myBinTree.root);    System.out.println();    myBinTree.postOrder2(myBinTree.root);    System.out.println();    myBinTree.levelTravel(myBinTree.root);}

}