建了一个JAVA二插树，不知道为什么运行过程中没有对应字符

Question

图在下面，希望来个大佬解决疑惑

Answer 1

参考：

public class Node {

    //数据域
    int data;
    //左孩子
    Node leftChild;
    //右孩子
    Node rightChild;
    
    public Node(int data) {
        this.data = data;
        leftChild = null;
        rightChild = null;
    }
}

public class BTree {

    //根节点
    Node root;
    public BTree(int data) {
        root = new Node(data);
    }
    //新增节点
    //10,8,7,20,90,100,3,6,1,-10
    public void addNode(int data){
        //获取根节点
        Node p=root;
        //生成新增节点
        Node t = new Node(data);
        while(true){
            //放到根节点的左边
            if(p.data>data){
                if(p.leftChild !=null){
                    //继续往下找
                    p = p.leftChild;
                }else{
                    p.leftChild = t;
                    break;
                }
            }else{//放到根节点的右边
                if(p.rightChild!=null){
                    p=p.rightChild;
                }else{
                    p.rightChild = t;
                    break;
                }
            }
        }
    }
    public void display(Node root){
        //先根遍历10,8,7,3,1，-10,6,20,90,100
        System.out.println(root.data);
        if(root.leftChild!=null){ //往左走
            System.out.println("往左走");
            display(root.leftChild);
        }
        //中根遍历：-10,1,3,6,7,8,10,20,90,100
//        System.out.println(root.data);
        if(root.rightChild!=null){//往右走
            System.out.println("往右走");
            display(root.rightChild);
        }
        //后根遍历：-10,1,6,3,7,8,100,90,20,10
//        System.out.println(root.data);
    }
    public static void main(String[] args) {
        //10,8,7,20,90,100,3,6,1,-10
        BTree tree = new BTree(10);
        tree.addNode(8);
        tree.addNode(7);
        tree.addNode(20);
        tree.addNode(90);
        tree.addNode(100);
        tree.addNode(3);
        tree.addNode(6);
        tree.addNode(1);
        tree.addNode(-10);
        tree.display(tree.root);
    }
}