我无法在Java中获得要打印的所有节点的平均值

// 定义树节点类
class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int val) {
        this.val = val;
    }
}

// 计算树节点平均值的方法
public double getAverage(TreeNode root) {
    if (root == null) {
        return 0;
    }

    int sum = getSum(root);
    int count = getCount(root);

    return (double) sum / count;
}

// 递归计算树节点值的总和
private int getSum(TreeNode node) {
    if (node == null) {
        return 0;
    }

    int leftSum = getSum(node.left);
    int rightSum = getSum(node.right);

    return node.val + leftSum + rightSum;
}

// 递归计算树节点的数量
private int getCount(TreeNode node) {
    if (node == null) {
        return 0;
    }

    int leftCount = getCount(node.left);
    int rightCount = getCount(node.right);

    return 1 + leftCount + rightCount;
}