java 实现基本二叉树操作

package train.demo;
import java.util.LinkedList;
import java.util.List;

public class tree {
    private int[] array = { 1, 2, 3, 4, 5, 6, 7, 8, 9 ,0};
    private static List<Node> nodeList = null;
    private static class Node {
        Node leftChild;
        Node rightChild;
        int data;

        Node(int newData) {
            leftChild = null;
            rightChild = null;
            data = newData;
        }
    }
    // 创建二叉树
    public void createBinTree() {
        nodeList = new LinkedList<>();
        for(int nodeIndex = 0; nodeIndex < array.length; nodeIndex++) {
            nodeList.add(new Node(array[nodeIndex]));
        }
        // 除最后一个父节点，可能只有左孩子，没有右孩子
        for (int parentIndex = 0; parentIndex < array.length / 2 - 1; parentIndex++) {
            // left
            nodeList.get(parentIndex).leftChild = nodeList.get(parentIndex * 2 + 1);
            // right
            nodeList.get(parentIndex).rightChild = nodeList.get(parentIndex * 2 + 2);
        }
        int lastParentIndex = array.length / 2 - 1;
        nodeList.get(lastParentIndex).leftChild = nodeList.get(lastParentIndex * 2 + 1);
        if (array.length % 2 == 1) {
            nodeList.get(lastParentIndex).rightChild = nodeList.get(lastParentIndex * 2 + 2);
        }
    }
    // 先序遍历
    public static void preOrderTraverse(Node node) {
        if (node == null) return;
        System.out.println(node.data + " ");
        preOrderTraverse(node.leftChild);
        preOrderTraverse(node.rightChild);
    }
    // 中序遍历
    public static void inOrderTraverse(Node node) {
        if (node == null)
            return;
        inOrderTraverse(node.leftChild);
        System.out.print(node.data + " ");
        inOrderTraverse(node.rightChild);
    }

    // 后序遍历
    public static void postOrderTraverse(Node node) {
        if (node == null)
            return;
        postOrderTraverse(node.leftChild);
        postOrderTraverse(node.rightChild);
        System.out.print(node.data + " ");
    }

    public static  void main(String args[]) {
        tree t = new tree();
        t.createBinTree();
        // 根节点
        Node root = nodeList.get(0);
        // 先序遍历
        preOrderTraverse(root);
    }

}