java双端链表

在这里插入代码片
package link01;

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 + "}");
	}
}

public class LinkList {
	private Link first;   // 引用链表的第一个引用
	private Link last; // 引用链表的最后一个引用
	
	public LinkList() {
		first = null;
		last = null;
	}
	
	public boolean isEmpty() {
		return (first == null);
	}
	
	public void insertFirst( int id, double dd) {
		Link newLink = new Link(id,dd);
		if ( isEmpty() )
			last = newLink;
		newLink.next = first;
		first = newLink;
	}
	
	public void insertLast(int id, double dd) {
		Link newLink = new Link(id,dd);
		if( isEmpty() ) {     // 边界判断，如果是第一个插入的元素，则头尾都指向同一个元素。
			first = newLink;
		}
		else
			last.next = newLink;
		last = newLink;
	}
	
	public Link deleteFirst() {
		Link temp = first;
		if( first.next == null ) // 边界，删除的是最后一个元素，last，first 都应该取消引用，让成为垃圾。
			last = null;
		first = first.next;
		return temp;
	}
	
	public void displayList() {
		System.out.println("List (first-->last)");
		Link current = first;
		while (current != null) {
			current.displayLink();
			current = current.next;
		}
	}
	
	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){  // 删除idate == key 的link。  对于双端链表来说，有点问题。如果链表只有一个元素的话，last 没有取消对它的引用。
		Link current = first;
		Link previous = first;
		while( current.iData != key) {
			if( current.next == null )
				return null;
			previous = current;
			current = current.next;
		}
		if ( current == first)
			first = first.next;
		else
			previous.next = current.next;
		return current;
	}
	
	
}

> https://blog.csdn.net/SHENGJINLI1/article/details/83175802