树的实现（树的创建及遍历）

节点Node：

package TreeExercise;

public class TreeNode<T> {
    public T data;
    public TreeNode<T> left;
    public TreeNode<T> right;

    public TreeNode(T t) {
        data = t;
        left = null;
        right = null;
    }
}

树的基本方法：

package TreeExercise;

import java.util.Scanner;

public class MyTree<T extends Comparable> {

    //根节点
    public TreeNode<T> root;

    public MyTree() {
        root = new TreeNode<T>(null);
    }

    //创建查找二叉树
    public void buildTree(TreeNode<T> node, T data) {
        if (root == null) {
            root = new TreeNode<T>(data);
        } else {
            if (data.compareTo(node.data) < 0) {
                if (node.left == null) {
                    node.left = new TreeNode<T>(data);
                } else {
                    buildTree(node, data);
                }
            } else {
                if (node.right == null) {
                    node.right = new TreeNode<T>(data);
                } else {
                    buildTree(node, data);
                }
            }
        }
    }

    public void createTree() {
        Scanner sanner = new Scanner(System.in);
        root = createTreeNode(root, sanner);
    }

    //前序遍历生成二叉树
    private TreeNode<T> createTreeNode(TreeNode<T> node, Scanner scanner) {
        T data = (T) scanner.nextLine();
        if ("/".equals(data)) {
            return null;
        } else {
            node = new TreeNode<T>(data);
            node.left = createTreeNode(node.left, scanner);
            node.right = createTreeNode(node.right, scanner);
        }
        return node;
    }


    //region 递归遍历二叉树

    //中序遍历
    public void orderTraverse() {
//        System.out.println("中序遍历");
        System.out.println("orderTraverse");
        orderTraverse(root);
        System.out.println();
    }

    private void orderTraverse(TreeNode<T> node) {
        if (node == null) return;

        orderTraverse(node.left);
        System.out.println((T) node.data);
        orderTraverse(node.right);
    }

    //前序遍历
    public void preOrderTraverse() {
//        System.out.println("前序遍历");
        System.out.println("orderTraverse");
        preOrderTraverse(root);
        System.out.println();
    }

    private void preOrderTraverse(TreeNode<T> node) {
        if (node == null) return;

        System.out.println(node.data);
        orderTraverse(node.left);
        orderTraverse(node.right);
    }

    //后序遍历
    public void postOrderTraverse() {
//        System.out.println("后序遍历");
        System.out.println("postOrderTraverse");
        postOrderTraverse(root);
        System.out.println();
    }

    private void postOrderTraverse(TreeNode<T> node) {
        if (node == null) return;

        orderTraverse(node.left);
        orderTraverse(node.right);
        System.out.println(node.data);
    }

    //endregion


}