Servlet网上售票问题引发线程安全问题的思考

package com.lc.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class Ticketsell extends HttpServlet { public int ticket = 3;//假设只有三张票   public void doGet(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException { PrintWriter out = response.getWriter(); response.setContentType("text/html;charset=gbk");   //简单点而处理售票问题 //当一个变量需要多个用户共享，则应该在访问该变量的时候加 同步机制 //如果一个变量不需要共享则直接在doGet()和doPost()方法中定义即可,这样的话就不存在线程的安全型问题   synchronized (this) { //解决同步性问题的方法    if(ticket > 0)  {  System.out.println("你买到票了！");  out.println("你买到票了！");    //休眠  try {   Thread.sleep(10*1000);  } catch (InterruptedException e) {   // TODO Auto-generated catch block   e.printStackTrace();  }  ticket--;  }  else  {  System.out.println("你没有买到票！");  out.println("你没有买到票！");  } }  }  public void doPost(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException {   this.doGet(request, response); }}