我被要求在 Java 中為學校“返回在二叉樹的前序遍歷中在節點 x 之后訪問的節點”。我已經創建了一個代碼來按預定順序列出所有節點，但我不確定如何打印單個節點。我創建節點的第一堂課是：public class TreeNode {int value;        // The data in this node.TreeNode left;   // Pointer to the left subtree.TreeNode right;  // Pointer to the right subtree.TreeNode parent; //Pointer to the parent of the node. TreeNode(int value) {    this.value = value;    this.right = null;    this.left = null;    this.parent = null; } public void displayNode() { //Displays the value of the node.    System.out.println(value + " "); }然后我有班級來構建二叉樹。它還按預定順序打印整棵樹：public class BTree2 {TreeNode root;                // the first node in the treepublic boolean isEmpty() // true if no links{    return root == null;}private TreeNode addRecursive(TreeNode current, int value) {    if (current == null) {        return new TreeNode(value);    }    if (value < current.value) {        current.left = addRecursive(current.left, value);    } else if (value > current.value) {        current.right = addRecursive(current.right, value);    } else {        // value already exists        return current;    }    return current;}public void add(int value) {    root = addRecursive(root, value);}void printPreorder(TreeNode node) {    if (node == null) {        return;    }    System.out.print(node.value + " "); /* first print data of node */    printPreorder(node.left);   /* then recur on left subtree */    printPreorder(node.right);  /* now recur on right subtree */}void printPreorder() {    printPreorder(root);}   這就是我卡住的地方：如何打印特定節點之后的節點，而不僅僅是整個樹？我以為會是： public TreeNode findPreorder(int key) // find node with given key  {                            // (assumes non-empty tree)      TreeNode current = root;                // start at root      while (current.value == key) // while there is a match      {        current = current.left;        if (key < current.value) // go left?          {            current = current.right;} 我的輸出是：二叉樹的前序遍歷為 1 2 4 5 31之后的節點是5有任何想法嗎？謝謝！！