下压堆栈（链表实现）

import java.util.Iterator;
public class Stack<Item>
{
    private Node first;   //栈顶
    private int N;        //元素数量
    private class Node
    {   //定义节点的嵌套类
        Item item;
        Node next;
    }
    public boolean isEmpty() {  return first == null; } // 或： N == 0
	public int size() {  return N; }
	public void push(Item item)
	{	// 向栈顶添加元素
		Node oldfirst = first;
		first = new Node();
		first.item = item;
		first.next = oldfirst;
		N++;
	}
	public Item pop()
	{	//从栈顶删除元素
		Item item = first.item;
		first = first.next;
		N--;
		return item;
	}
	public Iterator<Item> iterator()
	{	return new ListIterator();	}
	private class ListIterator implements Iterator<Item>
	{
		private Node current = first;
		public boolean hasNext()
		{	return current != null;	}
		public void remove() { }
		public Item next()
		{
			Item item = current.item;
			current = current.next;
			return item;
		}
	}       
}

　　队列的实现（链表）：

import java.util.Iterator;
public class Queue<Item>
{
    private Node first;   //指向最早添加的节点的链接
	private Node last;    //指向最近添加的节点的链接
    private int N;        //元素数量
    private class Node
    {   //定义节点的嵌套类
        Item item;
        Node next;
    }
    public boolean isEmpty() {  return first == null; } // 或： N == 0
	public int size() {  return N; }
	public void enqueue(Item item)
	{	//向表尾添加元素
		Node oldlast = last;
		last = new Node();
		last.item = item;
		last.next = null;
		if (isEmpty()) first = last;
		else	oldlast.next = last;
		N++;
	}
	public Item dequeue()
	{	//从表头删除元素
		Item item = first.item;
		first = first.next;
		if (isEmpty()) last = null;
		N--;
		return item;
	}
	public Iterator<Item> iterator()
	{	return new ListIterator();	}
	private class ListIterator implements Iterator<Item>
	{
		private Node current = first;
		public boolean hasNext()
		{	return current != null;	}
		public void remove() { }
		public Item next()
		{
			Item item = current.item;
			current = current.next;
			return item;
		}
	}
	public static void main(String[] args)
	{	//创建一个队列并操作字符串入列或出列
		Queue<String> q = new Queue<String>();
		while (!StdIn.isEmpty())
		{
			String item = StdIn.readString();
			if (!item.equals("-"))
				q.enqueue(item);
			else if (!q.isEmpty()) StdOut.print(q.dequeue() + " ");
		}
		StdOut.println("(" + q.size() + " left on queue)");
	}
}

　　包的实现（链表）：

import java.util.Iterator;
public class Bag<Item> impelements Iterable<Item>
{
    private Node first;   //链表的首节点
    private class Node
    {   
        Item item;
        Node next;
    }
	public void add(Item item)
	{	// 向栈顶添加元素
		Node oldfirst = first;
		first = new Node();
		first.item = item;
		first.next = oldfirst;
	}
	Iterator<Item> iterator()
	{	return new ListIterator();	}
	private class ListIterator implements Iterator<Item>
	{
		private Node current = first;
		public boolean hasNext()
		{	return current != null;	}
		public void remove() { }
		public Item next()
		{
			Item item = current.item;
			current = current.next;
			return item;
		}
	}       
}