java实现链表指定值得删除，查找第二部分代码

package com.liu.Link;

public class LinkList1 {
    private Link first;
    public LinkList1()
    {
        first = null;
    }
    
    public void insertFirst(int id,double dd)
    {
        Link newLink = new Link(id,dd);
        newLink.next = first;
        first = newLink;
    }
    
    public Link find(int key)
    {
        Link current = first;
        while(current.iData!=key)
        {
            if(current.next == null)
                return null;
            else
                current = current.next;
        }
        return current;
    }
    
    public Link delete(int key)
    {
        Link current = first;
        Link previous = first;
        while(current.iData != key)
        {
            if(current.next == null)
                return null;
            else
            {
                previous = current;
                current = current.next;
            }
        }
        //情况1，删除的数字就是first指针指向的位置
        if(current == first)
        {
            first = first.next;
        }
        //情况2，删除的数字是中间位置
        else
        {
            previous.next = current.next;
        }
        //current就是previous.next
        return current;
    }
    
    public void displayList()
    {
        System.out.print("List (first-->last):");
        Link current = first;
        while(current != null)
        {
            current.displayLink();
            current = current.next;
        }
        System.out.println("");
    }
}

//链表数据类
class Link
{
    public int iData;
    public double dData;
    public Link next;
    
    public Link(int id,double dd)
    {
        iData = id;
        dData = dd;
    }
    
    public void displayLink()
    {
        System.out.print("{"+ iData +", "+ dData +"}");
    }
    
}

class LinkListApp
{
    public static void main(String args[])
    {
        LinkList1 theList = new LinkList1();
        theList.insertFirst(22, 2.99);
        theList.insertFirst(44, 4.99);
        theList.insertFirst(66, 6.99);
        theList.insertFirst(88, 8.99);
        theList.insertFirst(33, 3.99);
        
        theList.displayList();
        
        Link f = theList.find(44);
        if(f!=null)
            System.out.println("Fount link with key "+f.iData);
        else
            System.out.println("can't find link");
        
        Link d = theList.delete(66);
        if( d != null )
             System.out.println("Deleted link with key " + d.iData);
          else
             System.out.println("Can't delete link");
        
        theList.displayList();
    }
}