java学习之—链表（2）

/**
 * 双端链表操作
 * Create by Administrator
 * 2018/6/14 0014
 * 下午 2:05
 **/
class Link1 {
 
    public long dData;
    public Link1 next;
 
    public Link1(int id) {
        this.dData = id;
    }
 
    public void displayLink() {
        System.out.print(dData + " ");
    }
}
 
public class FirstLastList {
 
    private Link1 first;
    private Link1 last;
 
    public FirstLastList() {
        this.first = null;
        this.last = null;
    }
 
    public boolean isEmpty(){           //判断链表是否为空
        return (first == null);
    }
 
    public long deleteFirst(){
        long temp = first.dData;
        if(first.next == null){
            last = null;
        }
        first = first.next;
        return temp;
    }
 
    public void insertFirst(int id){
        Link1 link = new Link1(id);
        if(isEmpty()){
            last = link;
        }
        link.next = first;          //储存对象的引用
        first = link;               //把当前对象赋值给first
    }
 
    public void  insertLast(int id){
        Link1 newLink = new Link1(id);
        if (isEmpty()){
            first = newLink;
        }else {
            last.next = newLink;
        }
        last = newLink;
    }
 
    public void displayList(){
        System.out.print("List (first-->last): ");
        Link1 current = first;
        while(current != null){
            current.displayLink();
            current = current.next;
        }
        System.out.println("");
    }
 
    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.displayList();
 
        theList.deleteFirst();
        theList.deleteFirst();
 
        theList.displayList();
    }
}