二叉树怎么打印，为什么图中的left和right会报红？

Question

import javax.swing.tree.TreeNode;  //这玩意儿也有导包，可以在非主方法里赋类型啥的
import java.util.ArrayList;
import java.util.List;

public class demoEz94 {  //深度优先搜索跟递归有关跟深度优先搜索也有关
    public static void main(String[] args) {
        Tree bt = new Tree();
        bt.createBinTree(bt.root);
    }



    public List<Integer> solution(TreeNode root){
        List<Integer> res = new ArrayList<Integer>();
        inorder(root, res);
        return res;

    }

    public void inorder(TreeNode root, List<Integer> res){
        if(root == null){
            return;
        }
        inorder(root.left, res);
        res.add(root.val);
        inorder(root.right, res);

    }
}

Answer 1

给你写了个树，然后按照二叉树排序了一个数组，然后按中序遍历打印树的结点值

public class Tree {

    public int value;
    public Tree left;
    public Tree right;

    Tree(int v) {
        value = v;
    }

    public void AddLeft(int v) {
        left = new Tree(v);
    }

    public void AddRight(int v) {
        right = new Tree(v);
    }

    public void Add(int v) {
        if (v < value) {
            if (left == null) {
                AddLeft(v);
            } else {
                left.Add(v);
            }
        } else {
            if (right == null) {
                AddRight(v);
            } else {
                right.Add(v);
            }
        }
    }

    public void Print() {
        if (left != null) {
            left.Print();
        }
        System.out.println(value);
        if (right != null) {
            right.Print();
        }
    }

    public static void main(String[] args) {
        int values[] = new int[] { 4, 2, 3, 1, 5, 6, 2, 7, 8 };
        Tree bt = new Tree(values[0]);
        for (int i = 1; i < values.length; i++) {
            bt.Add(values[i]);
        }
        bt.Print();
    }

}