处理 EmptyStackException

import java.util.EmptyStackException;
import java.util.Stack;

public class PreOrderTest {
    public static void main(String[] args) {
        /**
         * 解法一、递归法：要理解递归的思路并且熟练的使用它，就是要想清楚你想做什么，什么时候停止。
         *
         * 解法二、迭代法：用栈来模拟递归实现
         */

        int[] arr = {1,2,3,4,5,6,7};
        BinTree tree = new BinTree();
        tree.created(arr);
        preOrderInteraction01(tree.getRoot());
        System.out.println();
        try {
            preOrderInteraction02(tree.getRoot());
        } catch (EmptyStackException  e) {
            e.printStackTrace();
        }
    }

    public static void preOrderInteraction01(BinTree e) {
        if (e == null) {
            return;
        }

        // 1.遍历 处理（打印）根节点
        System.out.print(" " + e.val);
        // 1.遍历 处理（打印）左节点
        preOrderInteraction01(e.getlChild());
        // 1.遍历 处理（打印）右节点
        preOrderInteraction01(e.getrChild());
    }

    public static void preOrderInteraction02(BinTree r) throws EmptyStackException  {
        //校验数据
        if (r == null) {
            return;
        }

        Stack<BinTree> stack = new Stack<>();
        stack.push(r);
//        BinTree cur = r;
        while (stack != null) {
            BinTree cur = stack.pop();
            System.out.print(" " + cur.val);
            if (cur.getrChild() != null) {
                stack.push(cur.getrChild());
            }
            if (cur.getlChild() != null) {
                stack.push(cur.getlChild());
            }
        }
    }

}