链表_单链表（插入删除查询）

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

}

public class LinkList {
        public Link first;
        public LinkList() {
            first=null;
        }
        //是否为空
        public boolean isEmpty() {
            return first==null;
        }
        //插入
        public void insertFirst(int id,double dd) {
            Link newLink=new Link(id,dd);
            newLink.next=first;//插入头部，需要将next值为以前的first
            first=newLink;//改变frist为现在的插入
            
        }
        //删除头部
        public Link deleteFirst() {
            Link temp=first;
            first=first.next;//改变头
            return temp;
            
        }
        //查找
        public Link find(int key) {
            Link current=first;
            while(current.iData!=key) {
                if(current.next!=null) {
                    current=current.next;
                }else {
                    return null;
                }
            }
            return current;
        }
        //删除
        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;
                    
                }
            }
            if(current==first)
                first=first.next;
            else
                previous.next=current.next;
            return current;
        }
        //显示
        public void displayList() {
            Link current=first;
            while(current!=null) {
                current.displayLink();
                current=current.next;
            }
            System.out.println();
        }




}