userinfolist.java

自己写的具有图形界面的SMTP和POP3邮件服务器端程序,实现邮件发送和收取,新建用户功能,用最基本的语句描述了邮件服务器端与客户端之间的通信过程

package cstest;

import java.io.Serializable;

public class UserInfoList
        implements Serializable {
      Node root; //用户信息链表的跟
      Node pointer; //用于操作链表的游标
      int count;

      public UserInfoList() {
            root = new Node();
            root.next = null;

            pointer = null;
            count = 0; //初始元素个数0
      }

      public void add(Node n) {
            pointer = root; //将游标指向根节点

            while (pointer.next != null) { //判断是否链表尾部
                  pointer = pointer.next;
            }

            pointer.next = n; //加入节点
            n.next = null;
            count++; //计数器加1
      }

      public void del(Node n) {
            pointer = root; //将游标指向跟节点

            while (pointer.next != null) {
                  if (pointer.next == n) {
                        pointer.next = n.next; //删除节点
                        count--;

                        break;
                  }

                  pointer = pointer.next; // 将游标指向下一个节点
            }
      }

      //返回链表中的元素个数
      public int getCount() {
            return count;
      }

      public Node find(String username) {
            if (count == 0)
                  return null;
            pointer = root;

            while (pointer.next != null) { //判断是否到达链表尾部
                  pointer = pointer.next; //游标后移

                  if (pointer.UserName.equalsIgnoreCase(username)) {
                        return pointer; //返回找到的元素节点
                  }
            }

            return null;
      }

      public Node find(int index) {
            if (count == 0) {
                  return null;
            }

            if (index < 0) {
                  return null;
            }

            pointer = root;

            int i = 0;
            while (i < index + 1) {
                  if (pointer.next != null) {
                        pointer = pointer.next;
                  }
                  else {
                        return null;
                  }

                  i++;
            }

            return pointer;
      }
}