二叉排序樹的實現

問題表述：
二叉排序樹，如果左子樹不爲空，那麼左子樹上所有節點的值均小於其根結點的值；如果右子樹不爲空，那麼右子樹所有節點的值均大於其根結點的值；左右子樹也分別爲二叉排序樹。

代碼實現：

class Node{
    public int data;
    public Node left;
    public Node right;
    public Node(int data){
        this.data = data;
        this.left = null;
        this.right = null;
    }
}

public class BinaryTree {
    private Node root;
    public BinaryTree(){
        root = null;
    }
    //insert
    public void insert(int data) {
        Node newnode = new Node(data);
        if (root==null) {
            root = newnode;
        }else {
            Node current = root;
            Node parent;
            while (true) {
                parent = current;
                if (data<current.data) {
                    current = current.left;
                    if (current==null) {
                        parent.left = newnode;
                        return;
                    }
                }else {
                    current = current.right;
                    if (current==null) {
                        parent.right = newnode;
                        return;
                    }
                }
            }
        }
    }

    //build
    public void buildTree(int[] data) {
        for (int i = 0; i < data.length; i++) {
            insert(data[i]);
        }
    }

    //inOrder
    public void inOrder(Node localRoot) {
        if (localRoot!=null) {
            inOrder(localRoot.left);
            System.out.print(localRoot.data+" ");
            inOrder(localRoot.right);
        }
    }
    public void inOder() {
        inOrder(this.root);
    }

    //preOrder
    public void preOrder(Node localRoot) {
        if (localRoot!=null) {
            System.out.print(localRoot.data+" ");
            preOrder(localRoot.left);
            preOrder(localRoot.right);
        }
    }
    private void preOrder() {
        preOrder(this.root);
    }

    //postOrder
    public void postOrder(Node localRoot) {
        if (localRoot!=null) {
            postOrder(localRoot.left);
            postOrder(localRoot.right);
            System.out.print(localRoot.data+" ");
        }

    }
    public void postOrder() {
        postOrder(this.root);
    }

    public static void main(String[] args) {
        BinaryTree binaryTree = new BinaryTree();
        int[] data = {2,8,7,4,9,3,1,6,7,5};
        binaryTree.buildTree(data);
        System.out.print("inOrder is: ");
        binaryTree.inOder();
        System.out.println();
        System.out.print("preOrder is: ");
        binaryTree.preOrder();
        System.out.println();
        System.out.print("postOrder is: ");
        binaryTree.postOrder();
        System.out.println();
    }
}

運行結果：
inOrder is: 1 2 3 4 5 6 7 7 8 9
preOrder is: 2 1 8 7 4 3 6 5 7 9
postOrder is: 1 3 5 6 4 7 7 9 8 2