goring.java

该文件用JAVA实现的循环链表 是本人作业来的 用来实现从环中每格M个数就取出其中一个元素,直到环中所有元素为NU

import java.util.*;
class Ring extends java.util.AbstractSequentialList
{
  private Node header;
  private int size =0;
  
  public Ring()
  {}
  
  public Ring(List list)
  {
       super();
       addAll(list);
  }
  
  public ListIterator listIterator(int index)
  {
     return new RingIterator(index);
  }
  
  public int size()
  {
        return size;
  }
  
  private static class Node
  {
        Object object;
        Node previous , next;
        
        Node(Object object,Node previous,Node next)
        {
         this.object=object;
         this.previous = previous;
         this.next = next;
        }
        
        Node(Object object)
        {
         this.object = object;
         this.previous = this.next = this;
        }
        
  }
  private  class RingIterator implements ListIterator
  {
     private Node next,lastReturned;
     private int nextIndex;
     
     RingIterator(int index)
     {
       if(index<0 || index > size) System.out.print("ddd");
       next=(size==0?null:header);
       for(nextIndex =0;nextIndex<index;nextIndex++)
          next= next.next;
     }
     
     public boolean hasNext()
     {
         return size>0;
     }
     
     public boolean hasPrevious()
     {
          return size >0;
     }
     
     public Object next()
     {
      if (size==0)  throw  new NoSuchElementException();
      lastReturned = next;
      next=next.next;
      nextIndex=(nextIndex==0?size-1:nextIndex-1);
      return lastReturned.object;
     }
     
     public Object previous()
     {
       if(size ==0) throw  new NoSuchElementException();
       next = lastReturned = next.previous;
       nextIndex = (nextIndex==0?size -1:nextIndex-1);
       return lastReturned.object;	
     }
     
     
     public int nextIndex()
     {
       return nextIndex;
     
     }
     
     public int previousIndex()
     {
       return (nextIndex==0?size -1:nextIndex -1);
     }
     
     public void add(Object object)
     {
        if(size==0)
        {
         next =header=new Node(object);
         nextIndex =0;
        }
        else
        {
         Node newNode = new Node(object,next.previous,next);
         newNode.previous.next= next.previous= newNode;
        }
        lastReturned =null;
        ++size;
        nextIndex=(nextIndex==size-1?0:nextIndex+1);
     }
     
     public void remove()
     {
       if (lastReturned ==null ) throw  new IllegalStateException();
       if (next==lastReturned) next=lastReturned.next;
       else nextIndex = (nextIndex ==0?size -1:nextIndex-1);
       lastReturned.previous.next= lastReturned.next;
       lastReturned.next.previous =lastReturned.previous;
       lastReturned = null;
       -- size;
       
      }
       public void set(Object object)
       {
        if ( lastReturned ==null ) throw new IllegalStateException();
        lastReturned.object = object;
       
       }
     
     
  }
}
public class goRing
{
      private static final int SIZE =8;
      private static Ring ring = new Ring();
     
      
      public static void main(String agrs[])
      {
          ListIterator it = ring.listIterator();
          for(int n=0;n<SIZE;n++)
            it.add(new Integer (n) );
          printNext(it,5); 
          
      	
      }	
      private static void printNext(ListIterator it,int m )
      {
        int n=5;
        Object keeppoint=new Object();
        
        for(int k=0;n<SIZE;k ++)
        {
        for(int i=0;i<n;i++ )	
        keeppoint =it.next();
        System.out.println("it:="+keeppoint);
        it.remove();  
        }
         
      }
}