linkedlist.java

JSP聊天系统

package org.ehotsoft.yekki.util.link;

public class LinkedList {

    private LinkedListNode head = new LinkedListNode( "head", null, null );

    public LinkedList() {
        head.next = head.previous = head;
    }

    public LinkedListNode getFirst() {
        
		LinkedListNode node = head.next;
        
		if (node == head) {
        
			return null;
        }

        return node;
    }

    public LinkedListNode getLast() {
        LinkedListNode node = head.previous;
        if (node == head) {
            return null;
        }
        return node;
    }

	public LinkedListNode addFirst( LinkedListNode node ) {

        node.next = head.next;
        node.previous = head;
        node.previous.next = node;
        node.next.previous = node;

        return node;
    }

    public LinkedListNode addFirst( Object object ) {

        LinkedListNode node = new LinkedListNode(object, head.next, head);
        node.previous.next = node;
        node.next.previous = node;

        return node;
    }

    public LinkedListNode addLast( Object object ) {

        LinkedListNode node = new LinkedListNode(object, head, head.previous);
        node.previous.next = node;
        node.next.previous = node;

        return node;
    }

    public void clear() {

        LinkedListNode node = getLast();

        while (node != null) {

            node.remove();
            node = getLast();
        }

         head.next = head.previous = head;
    }

	public String toString() {

        LinkedListNode node = head.next;
        StringBuffer buf = new StringBuffer();

        while (node != head) {

            buf.append(node.toString()).append(", ");
            node = node.next;
        }

        return buf.toString();
    }
}