Java迭代器中单链表的实现

Question

current.item = item;
Node<T> nextNode = new Node<T>();
current.next = nextNode;
current = nextNode;

当前:Bag$Node@1786F9D5下一个:Bag$Node@704D6E83

看起来很清楚，至少在我看来，下一个节点每次都会设置一个新节点。我将所有四个元素都添加到包中，但条目丢失，并为每个索引返回null。toArray（）函数显示[null,null,null,null]

我敢肯定这是一件简单得让人眼花缭乱的事情。下面是整个实现。

import java.util.Iterator;

public class Bag<T> implements Iterable<T> {
    private Node current;
    //Node<T> head;
    private int numberofProducts;
    T[] myBag;
    int defaultCapacity;

    public Iterator<T> iterator() {
        return new ListIterator<T>(current);
    }

    public Bag(int defaultCapacity) {
        this.current = new Node<T>();
        this.numberofProducts = 0;
        this.defaultCapacity = defaultCapacity;
    }

    public void add(T item) {
        if(isFull()) {
            System.out.println("bags full, yo");
            return;
        }

        current.item = item;
        Node<T> nextNode = new Node<T>();
        current.next = nextNode;
        current = nextNode;

        numberofProducts++;

    //Node<T> nextNode = current;
    //current = new Node<T>();
    //current.item = item;
    //current.next = nextNode;
    //numberofProducts++;


    }

    public Object[] toArray() {
        Object[] array = new Object[size()];

        int i = 0;
        Node<T> node = current;
        //Node<T> node = head;
        while(node.next != null) {
            array[i] = node.item;
            node = node.next;
            i++;
        }

        return array;
    }

    public boolean isEmpty() {
        return this.numberofProducts <= 0;
    }

    public boolean isFull() {
        return this.numberofProducts >= defaultCapacity;
    }

    public int size() {
        return this.numberofProducts;
    }

    private class Node<T> {
        private T item;
        private Node<T> next;
    }


    private class ListIterator<T> implements Iterator<T> {

        private Node<T> current;

        public  ListIterator(Node<T> first) {
            current = first;
        }

        public boolean hasNext() {

            return current != null;
        }

        public T next() {
            if(hasNext()) {
                T item = current.item;
                current = current.next;
                return item;
            }
            return null;
        }

        public void remove() {

        }
    }
}