Algs4-1.3.42复制栈

1.3.42复制栈。为基于链表产现的栈编写一个新的构造函数，使以下代码Stack<Item> t=new Stack<Item>(s);得到的t指向栈s的一个新的独立的副本。
答：

import java.util.Iterator;
public class Stack<Item> implements Iterable<Item>
{
    private int N;
    private Node first;
    private class Node
    {
        Item item;
        Node next;
    }

    public Stack()
    {
    }

    public Stack(Stack s)
    {
        Node right=new Node();
        Node oldright;
        for(Object i:s)
        {
            oldright=right;
            right=new Node();
            right.item=(Item) i;
            right.next=null;
            if(isEmpty())
               first=right;
            else
               oldright.next=right;
            N++;
         }
    }
    public boolean isEmpty()
    {return N==0;}

    public int size()
    {return N;}

    public void push(Item item)
    {
        Node oldfirst=first;
        first=new Node();
        first.item=item;
        first.next=oldfirst;
        N++;
    }

    public Item pop()
    {
        Item item=first.item;
        first=first.next;
        N--;
        return item;
    }


    public Item peek()
    {
        Item item=first.item;
        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;
        }//end next
    }//end class ListIterator

    public static void main(String[] args)
    {
        Stack<String> s=new Stack<String>();
        while(!StdIn.isEmpty())
        {
            String item=StdIn.readString();
            s.push(item);
        } //end while
        StdOut.println("---Stack s is:");
        for(String i:s)
            StdOut.print(i+" ");


        Stack<String> t=new Stack<String>(s);
        StdOut.println();
        StdOut.println("---Stack after new Stack<String>(s) is:");
        for(String i:s)
            StdOut.print(i+" ");
        //
        s.pop();
        StdOut.println();
        StdOut.println("---Stack after s pop, s is:");
        for(String i:s)
            StdOut.print(i+ " ");
        //
        StdOut.println();
        StdOut.println("---Stack t is:");
        for(String i:t)
            StdOut.print(i+" ");
       }
}