为什么在我的LinkedBinaryTree实现中只添加根目录

这是我的密码。LinkedBinaryTree和Position类来自教科书,如果需要,我可以为它们提供代码,但我不确定这是否必要。这个类应该能够向二叉树中添加一个新节点,这样对于每个内部节点,存储在父节点左侧的元素小于父节点的元素,存储在父节点右侧的元素大于父节点,因此它应该创建一个二叉搜索树。问题是,当我打印出结果树(见下文)时,我只得到根元素。

import net.datastructures.LinkedBinaryTree;
import net.datastructures.Position;

import java.util.Iterator;

public class IntLinkedBinaryTree extends LinkedBinaryTree<Integer> {


// define instance variables and methods, including a constructor(s) as needed
private Position<Integer> root;
private int size;

/**
 * Creates an empty IntLinkedBinaryTree
 */
public IntLinkedBinaryTree() {
    root = null;
    size = 0;
}

/**
 * Add a new node with e to the tree rooted at position p
 *
 * @param p The root of the tree to which new node is added
 * @param e The element of the new node
 * @return If a node with e does not exist, a new node with e is added and
 * reference to the node is returned. If a node with e exists, null is returned.
 */
public Position<Integer> add(Position<Integer> p, Integer e) {

    if (p == null) {
        root = addRoot(e);
        size++;
        return p;
    }
    Position<Integer> x = p;
    Position<Integer> y = x;
    while (x != null) {
        if (x.getElement().equals(e)) {
            return null;
        } else if (x.getElement() > e) {
            y = x;
            x = left(x);
        } else {
            y = x;
            x = right(x);
        }
    }   // end while
    Position<Integer> temp;
    if (y.getElement() > e) {
        temp = createNode(e, validate(y), null, null);
        addLeft(temp, e);
    } else {
        temp = createNode(e, validate(y), null, null);
        addRight(temp, e);
    }
    size++;
    return temp;
}


public static void main(String[] args) {

    // create a new binary tree instance
    IntLinkedBinaryTree t = new IntLinkedBinaryTree();

    // add some integers
    t.add(t.root, 100);

    t.add(t.root, 50);

    t.add(t.root, 150);

    t.add(t.root, 70);

    // print all integers in the tree in increasing order
    // after adding above four integers, the following should be printed
    // 50 70 100 150

    Iterator<Position<Integer>> it = t.inorder().iterator();
    System.out.println();
    while (it.hasNext()) {
        System.out.print(it.next().getElement() + " ");
    }
    System.out.println();
  }
}

我的产出只有100英镑,我要把头发拔出来了。讲师在LinkedBinaryTree类中提供了addRoot()、addLeft()和addRight()、inorder()和iterator()方法,整个main方法也是。当我使用intelliJ调试代码时,它调用了add*方法,但只向控制台打印了100次。