Java数据结构——双端链表

 

class FirstLastList{
	private Link first;
	private Link last;
	
	public FirstLastList() {	//构造函数
		this.first = null;
		this.last = null;
	}
	
	public boolean isEmpty(){
		return (first == null);
	}
	
	public void insertFirst(int id,double dd){		//从链表的头开始插入
		Link newLink = new Link(id,dd);
		if(isEmpty()){
			last = newLink;				//不用改变first
		}
		newLink.next = first;
		first = newLink;
	}
	
	public void insertLast(int id,double dd){	//从链表的尾开始插入
		Link newLink = new Link(id,dd);
		if(isEmpty()){
			first = newLink;		//不用改变last
		}else{
			last.next = newLink;		//在last后面添加新元素，并修改last的位置
		}
		last = newLink;				//注意：只有一个元素的时候，插入要把last也赋为newLink
	}
	
	public Link deleteFirst(){
		Link temp = first;		//暂存first
		if(first.next == null){		//如果只有一个元素，把last也赋为null
			last = null;
		}
		first = first.next;			//把next设为first
		return temp;				//返回原来的first
	}
	
	public void displayList(){
		System.out.println("List(first-->last):");
		Link current = first;			//用于不断改变位置实现遍历
		while(current != null){
			current.displayLink();
			current = current.next;
		}
	}
	
}

public class FirstLastList_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		FirstLastList theList = new FirstLastList();
		theList.insertFirst(11, 11.1);
		theList.insertFirst(22, 22.2);
		theList.insertFirst(33, 33.3);
		theList.insertFirst(44, 44.4);
		theList.insertFirst(55, 55.5);
		theList.displayList();
		
		theList.deleteFirst();
		theList.deleteFirst();
		theList.deleteFirst();
		theList.displayList();
		
	}

}