BST中的等级遍历。队列没有合作

Question

问题是我的链接队列列表没有合作。我已经盯着这一段时间，但无法弄清楚为什么我的优惠没有通过。

第一组代码在MyBST中。具有左和右元素的节点标记为TreeNodes。我创建了一个TreeNodes的Linked Queue，希望它们在通过队列时保留它们的左/右指针。我现在要发表评论......

private void traversalBreadth(TreeNode<E> current) 
{
    if(current==null)return;
    MyLinkedQueue<TreeNode<E>> q = new MyLinkedQueue<TreeNode<E>>();
    q.offer(current);//goes through fine and is able to start the while loop 
    //with no issues.
    while(q.isEmpty()==false) 
    {
        current= (TreeNode<E>) q.poll();//so that the loop prints the current element.
        System.out.println(current.element); //where each level will print
        if(current.left!=null) 
        {
            //Problem is here. I am offering the left element of my BST but nothing is actually in the queue. 
            q.offer(current.left);
            //I tried printing current.left.element and current.right.element and they always work with no issue. i am not sure why i cannot offer it to my queue.
            System.out.println(q.peek());//checking to see if anything here but nothing. 
        }
        if(current.right!=null) 
        {
            q.offer(current.right);
        }
    }
}

链接队列以防出现问题：

package HW8;


public class MyLinkedQueue<E> {
    QueueNode<E> head,tail;

    MyLinkedQueue(){    
    }

    MyLinkedQueue(E[] objects)
    {
        for(E e: objects)
            offer(e);

    }

    class QueueNode<E>
    {
        E element;
        QueueNode <E> next;
        public QueueNode(E element){
            this.element=element;
        }
    }

    E poll() {
        if(head==null) return null;
        QueueNode<E> tmp = head;
        head = head.next;
        //head.previous = null;
        return tmp.element;
    }

    E peek() {
        if(head==null) return null;
        return head.element;
    }

    void offer(E e) {
        QueueNode<E> newNode = new QueueNode<>(e);
        if(tail==null)
        {
            head=tail=new QueueNode<>(e);
        }
        else{
            tail.next = newNode;
            tail = newNode;
        }
    }

    boolean isPalin() {

        if(head!=tail) 
        {
            return false;
        }
        else {
            boolean first = true;
            QueueNode<E> current = head;
            QueueNode<E> backwards = tail;
            while(current!=tail) {
                current = current.next; 
            }
        }

        return false;
    }

    boolean isEmpty() {
        if(head==null||tail==null) 
            return true;
        else 
            return false;
    }
}

EDIT1： 主要代码只是

 Integer a[] = { 22, 3, 8, 16, 64, 7, 18 , 
                    -3, 23, -10, -1, 25, 20, 9};

    MyBST test = new MyBST(a);
    test.breadthOrder();

输出22,3，null。 null是从我试图查看队列时开始的。