数据结构java实现之双端链表

package com.liu.Link;

//双端链表
public class FirstLastList {
    private LinkLast first;
    private LinkLast last;
    public FirstLastList()
    {
        first = null;
        last = null;
    }
    
    public boolean isEmpty()
    {
        return first == null;
    }
    
    public void insertFirst(long d)
    {
        LinkLast newLink = new LinkLast(d);
        if(isEmpty())
        {
            last = newLink;
        }
        newLink.next = first;
        first = newLink;
    }
    
    public long deleteFirst()
    {
        long temp = first.dData;
        if(first.next == null)
            last = null;
        first = first.next;
        return temp;
    }
    
    public void insertLast(long d)
    {
        LinkLast newLink = new LinkLast(d);
        if(isEmpty())
        {
            first = newLink;
        }else
        {
            last.next = newLink;
        }
        last = newLink;
    }
    
    public void displayLast()
    {
        System.out.print("List (first-->last):");
        LinkLast current = first;
        while(current!=null)
        {
            current.display();
            current = current.next;
        }
        System.out.println();
    }
}
class LinkLast
{
    public long dData;
    public LinkLast next;
    
    public LinkLast(long dd)
    {
        dData = dd;
    }
    
    public void display()
    {
        System.out.print(dData+" ");
    }
}

class FirstLastApp
{
    public static void main(String[] args)
    {
        FirstLastList theList = new FirstLastList();
        theList.insertFirst(22);
        theList.insertFirst(44);
        theList.insertFirst(66);
        
        theList.insertLast(11);
        theList.insertLast(33);
        theList.insertLast(55);
        
        theList.displayLast();
        theList.deleteFirst();
        theList.deleteFirst();
        
        theList.displayLast();
    }
}