Algs4-1.3链表实现科泛型可迭代Bag

 
import java.util.Iterator;
public class Bag<Item> implements Iterable<Item>
{
    private Node first;
    private int N;
    private class Node
    {
        Item item;
        Node next;
    }//end class Node
    public boolean isEmpty(){return N==0;}
    public int size(){return N;}
    public void add(Item item)
    {
        Node oldfirst=first;
        first=new Node();
        first.item=item;
        first.next=oldfirst;
        N++;
    }//end add
   
    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)
    {
        Bag<String> b=new Bag<String>();
        while(!StdIn.isEmpty())
        {
            String item=StdIn.readString();
            b.add(item);
        }//end while
        for(String item:b)
            StdOut.print(item+" ");
    }//end main
   
   
}