尾插法实现LinkedList

本科时学习数据结构一直是使用c语言，最近想到使用java实现尾插法链表会是什么样的效果呢，于是编写了一个简单的尾插法LinkedList，实现了迭代器，增加，删除，插入。供参考：

import java.util.Iterator;

/**
 * Created by wzy on 17-2-24.
 */
public class MyLinkedList<T> implements Iterable<T>{

    public static class Node<U>{
        U item;
        Node<U> next;

        public Node(){
            item = null;
            next = null;
        }

        public Node(U item, Node<U> next){
            this.item = item;
            this.next = next;
        }
    }

    private Node<T> top = new Node<T>();

    private Node<T> node = top;


    public void add(T item){
        node.next = new Node<T>(item, null);
        node = node.next;
    }

    public void insert(int index, T item){
        int i = -1;
        Node<T> pre = null;
        Node<T> now = null;
        now = top;

        while(i < index){
            pre = now;
            now = now.next;
            i++;
            if (i > index && now == null){
                throw new RuntimeException("index error");
            }
        }
        pre.next = new Node<T>(item, now);
    }

    public void remove(int index){
        int i = -1;
        Node<T> pre = null;
        Node<T> now = null;
        now = top;

        while(i < index){
            pre = now;
            now = now.next;
            i++;
            if (i > index && now == null){
                throw new RuntimeException("index error");
            }
        }
        pre.next = now.next;

    }

    @Override
    public Iterator<T> iterator() {
        return new Iterator<T>() {

            Node<T> now = top;

            @Override
            public boolean hasNext() {
                return now.next != null;
            }

            @Override
            public T next() {
                now = now.next;
                return now.item;
            }
        };
    }

    @Override
    public String toString() {
        StringBuffer stringBuffer = new StringBuffer("{");
        node = top.next;
        while(node != null){
            stringBuffer.append(node.item + ", ");
            node = node.next;
        }
        stringBuffer.delete(stringBuffer.length() -2 , stringBuffer.length());
        stringBuffer.append("}");
        return stringBuffer.toString();
    }

    public static void main(String[] args) {
        MyLinkedList<String> list = new MyLinkedList<>();

        list.add("1");
        list.add("2");
        list.add("3");
        System.out.println(list);
        list.insert(1, "4");
        list.insert(4, "5");
        System.out.println(list);
        list.remove(4);
        System.out.println(list);

        for (String s : list){
            System.out.println(s);
        }

    }/*output:
		{1, 2, 3}
		{1, 4, 2, 3, 5}
		{1, 4, 2, 3}
		1
		4
		2
		3
	*/
}