I m trying to write an implementation of iterator so that I can call it within my BST class, under iterator() method.

My solution (not sure if it would work correctly) is to use a stack or a queue to store the nodes of the BST. Trouble is, my Iterator Implementation class can t recognise my BST nodes when I pass the "root" node into its constructor.

为了便于想象，这是我的BST实现，它适用于其他方法，包括添加、删除等。但我目前只能使用迭代器（）方法。因为我不知道该怎么开始，该怎么办。

   public class DictionaryImp<E extends Comparable<E>> implements Dictionary<E> {

        public class DictNode {
           public DictNode left;
           public DictNode right;
           public String position;
           public E value;

           public DictNode(E value, DictNode left, DictNode right, String position) {
               this.left = left;
               this.right = right;
               this.position = position;
               this.value = value;
           }
        }

       public DictNode root;

       //... more code

       public Iterator<E> iterator() {
             // provides a fail fast iterator for the Dictionary
             // starting at the least element greater than or equal to start
             Iterable<E> itr = new DictionaryItr<E>(root);
             Iterator<E> it = itr.iterator();
             return it;
       }
}

这是我为Iterator实现编写的

public class DictionaryItr<E> implements Iterable<E> {
    public DictionaryItr(DictNode root) {
        first = null;
        this.inOrderTraversial(root);
    }

    public void inOrderTraversial(DictNode node) {
        if (node != null) {
            inOrderTraversial(node.left);
            first.push(node.value);
            inOrderTraversial(node.right);
        }
    }

    // more code: push, peek, pop

    public Iterator<E> iterator() {
        return new ListIterator();
    }
    private class ListIterator implements Iterator<E> {
        private Node current = first;
        public boolean hasNext()  { return current != null;                     }
        public void remove()      { throw new UnsupportedOperationException();  }

        public E next() {
            if (!hasNext()) throw new NoSuchElementException();
            E item = current.item;
            current = current.next; 
            return item;
        }
    }
}