循环单链表

Question

I have been trying to make a Circular Linked List in Java. I believe that I am inserting properly, but I cannot get my delete or display to work properly. This is my code.

public class Link
{
  public int data; 
  public Link next;

 public Link(int d)
  {
     data = d;  //store data
     next = null; //set next Link to newLink
  }
}

   public class IntListCircularCount
  {
  private Link first;//this always points to the first link.
  private Link current=null;
  private int count =0;

  public IntListCircularCount()
  {
     first = null;
  }

  public boolean isEmpty()
  {
     return (first==null);
  }

  public Link getFirst()
  {
     return first;
  }   

  public void insert(int n)
  {
     if(count == 0)
     {
        Link newLink = new Link(n);
        first=newLink;
        count++;
        current = first;       
     }
     else if(count>0)
     {
        Link newLink = new Link(n);
        first.next = newLink;
        newLink.next = first;
        count++;
        current = first.next;
     }
  }

  public void display(int width)
  {
     if(isEmpty())
        System.out.printf("%" + width + "s", "--");
     else if(count ==1)
        System.out.printf("%" + width + "d",first.data);
     else if(!isEmpty() && first.next !=first)
     {
        while (first !=current)
        {       
           System.out.printf("%" + width + "d", current.data);
           current = current.next;
        }
     }   
  }

  public void delete()
  {
     if(count==0)
     {
        first=null;
     }
     else if(count==1)
     {            
        first = first.next;
     }
     else if(count>1)
     {
        current.next=first.next;
        first = first.next;
        count--;
     }
    }
 }


  public class IntListUser
 {
  public static void main (String[] args)
  {
     final int n =5;//there will be n Links
     final int w=5; //field width for display
     IntListCircularCount list = new IntListCircularCount();
     for(int i=1; i<=n; i++)
     {
        list.display(w);
        list.insert(10*i);
     }
     list.display(w);


     System.out.println("  -------------end of inserting ----------------");
     list.delete();
     list.display(w);
         list.delete();
     list.display(w);
        list.delete();
     list.display(w);
        list.delete();
     list.display(w);
        list.delete();
     list.display(w);
  }
  }

Answer 1

I usually do some napking sketches before writing any code. They save me a lot of trouble.

Ok, but for your question:

Your insert is only inserting after the first element. If your current points to the end, then when you insert a new element it should be linked to current, not to first. And current should always point to first (to make the list circular), even with just one element.

public void insert(int n)
  {
  if(count == 0)
  {
     Link newLink = new Link(n);
     first=newLink;
     count++;
     current = first;
     current.next = first;     
  }
  else
  {
     Link newLink = new Link(n);
     current.next = newLink;
     newLink.next = first;
     count++;
     current = current.next;
  }
}

Also, your display needs to display from first to current, but you shouldn't lost first and current.

public void display(int width)
{
   Link display_me = first;
   if(isEmpty())
      System.out.printf("%" + width + "s", "--");
   else 
   {
      Link display_me = first;
      do {       
         System.out.printf("%" + width + "d", current.data);
         display_me= display_me.next;
      } while (first != display_me);

   }   
}

As for the delete, I don't know if you want to delete the first or the current.

Hope this helps.