C#中一道关于线程同步的练习题——模拟多窗口售票

2021-07-12 08:17:13

题目：模拟窗口卖票，四个窗口同时对外开放售票，需要按顺序售出。

要求：输出每一张票的售出时间和售出窗口，不能出现票未售出或者被售出多次的情况。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.IO;
using System.Reflection;
using System.Diagnostics;

namespace SellTicketsSynchronously
{
    class Program
    {
        //入口
        static void Main(string[] args)
        {
            Ticket tc = new Ticket(10);
            Thread sellWindowA = new Thread(new ParameterizedThreadStart(SellTicket));
            Thread sellWindowB = new Thread(new ParameterizedThreadStart(SellTicket));
            Thread sellWindowC = new Thread(new ParameterizedThreadStart(SellTicket));
            Thread sellWindowD = new Thread(new ParameterizedThreadStart(SellTicket));
            sellWindowA.Name = "Window A";
            sellWindowB.Name = "Window B";
            sellWindowC.Name = "Window C";
            sellWindowD.Name = "Window D";
            sellWindowA.Start(tc);
            sellWindowB.Start(tc);
            sellWindowC.Start(tc);
            sellWindowD.Start(tc);
            sellWindowA.Join();
            sellWindowB.Join();
            sellWindowC.Join();
            sellWindowD.Join();
            Console.WriteLine("Tickets has been sold out. Press any key to quit:");
            Console.ReadLine();
        }
        //卖票方法
        public static void SellTicket(object obj) 
        {
            Ticket ticket = obj as Ticket;
            while (ticket.NumOfTickets>0)
            {
                lock (ticket)
                {
                    if (ticket.NumOfTickets > 0)
                    {
                        try
                        {
                            ticket.NumOfTickets--;
                            Console.WriteLine( DateTime.Now.ToString()+":"+Thread.CurrentThread.Name + " sells a ticket, " + ticket.NumOfTickets + " tickets left.");
                        }
                        catch (Exception ex)
                        {
                            WriteLog(ex);
                        }
                    }
                }
                Random random = new Random();
                Thread.Sleep(random.Next(100,500));
            } 
        }
        //打log方法
        private static void WriteLog(Exception ex)
        {
            string logUrl = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) + "\\SellTicketslog.txt";
            if (File.Exists(@logUrl))
            {
                using (FileStream fs = new FileStream(logUrl, FileMode.Append))
                {
                    using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
                    {
                        try
                        {
                            sw.Write(ex);
                        }
                        catch (Exception ex1)
                        {
                            WriteLog(ex1);
                        }
                        finally
                        {
                            sw.Close();
                            fs.Close();
                        }
                    }
                }
            }
            else
            {
                using (FileStream fs = new FileStream(logUrl, FileMode.CreateNew))
                {
                    using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
                    {
                        try
                        {
                            sw.Write(ex);
                        }
                        catch (Exception ex1)
                        {
                            WriteLog(ex1);
                        }
                        finally
                        {
                            sw.Close();
                            fs.Close();
                        }
                    }
                }
            }
        }
    }
    //票类
    class Ticket 
    {
        public int NumOfTickets { get; set; }
        public Ticket(int num) 
        {
            this.NumOfTickets = num;
        }
    }
}

运行结果：

不知道这么写会不会有问题，求指点。

————————修改版——————————

经过园友指点，我改用了Task写了这段代码，其间得到了园友的帮助，非常感谢！

修改后的代码如下（蓝色字体为修改的部分）：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.IO;
using System.Reflection;
using System.Diagnostics;

namespace SellTicketsSynchronously
{
    class Program
    {
        //入口
        static void Main(string[] args)
        {
            Ticket tc = new Ticket(10);
            WaitForAllSales(tc);
            Console.WriteLine("Tickets has been sold out. Press any key to quit:");
            Console.ReadLine();
        }
        //售罄方法
        private static void WaitForAllSales(Ticket tc) 
        {
            //创建一个Task类型的泛型list
            List<Task> tasks = new List<Task>();
            for (int i = 1; i <= 4; i++)
            {
                //将所有的售票task存入list
                tasks.Add(Task.Run(() => { SellTicket(string.Format("Window"+i), tc); }));
            }
            //等待所有的task都完成
            Task.WaitAll(tasks.ToArray());
        }
        //卖票方法
        public static void SellTicket(string windowName, object obj) 
        {
            string nameOfWindow = windowName;
            Ticket ticket = obj as Ticket;
            while (ticket.NumOfTickets > 0)
            {
                lock (ticket)
                {
                    if (ticket.NumOfTickets > 0)
                    {
                        try
                        {
                            ticket.NumOfTickets--;
                            Console.WriteLine(DateTime.Now.ToString() + ":" + nameOfWindow + " sells a ticket, " + ticket.NumOfTickets + " tickets left.");
                        }
                        catch (Exception ex)
                        {
                            WriteLog(ex);
                        }
                    }
                }
                Random random = new Random();
                Thread.Sleep(random.Next(100,500));
            }
        }
        //打log方法
        private static void WriteLog(Exception ex)
        {
            string logUrl = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) + "\\SellTicketslog.txt";
            if (File.Exists(@logUrl))
            {
                using (FileStream fs = new FileStream(logUrl, FileMode.Append))
                {
                    using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
                    {
                        try
                        {
                            sw.Write(ex);
                        }
                        catch (Exception ex1)
                        {
                            WriteLog(ex1);
                        }
                        finally
                        {
                            sw.Close();
                            fs.Close();
                        }
                    }
                }
            }
            else
            {
                using (FileStream fs = new FileStream(logUrl, FileMode.CreateNew))
                {
                    using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
                    {
                        try
                        {
                            sw.Write(ex);
                        }
                        catch (Exception ex1)
                        {
                            WriteLog(ex1);
                        }
                        finally
                        {
                            sw.Close();
                            fs.Close();
                        }
                    }
                }
            }
        }
    }
    //票类
    class Ticket 
    {
        public int NumOfTickets { get; set; }
        public Ticket(int num) 
        {
            this.NumOfTickets = num;
        }
    }
}

运行结果：

欢迎大家发散思维，继续提出宝贵意见！:)

------------------------------------------------------------------------------------------------------------

经过一位朋友细心的发现，上面这个程序逻辑是有问题的，一直都是售票窗口5在售票，修改后的代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.IO;
using System.Reflection;
using System.Diagnostics;

namespace SellTicketsSynchronously
{
    class Program
    {
        //入口
        static void Main(string[] args)
        {
            Ticket tc = new Ticket(20);
            WaitForAllSales(tc);       
            Console.ReadLine();
        }
        //售罄方法
        private static void WaitForAllSales(Ticket tc) 
        {
            //创建一个Task类型的泛型list
            List<Task> tasks = new List<Task>();
            System.Random ran = new Random();
            while (tc.NumOfTickets > 0)
            {
                int i = ran.Next(1,6);
                //将所有的售票task存入list
                tasks.Add(Task.Run(() => { SellTicket(string.Format("Window" + i), tc); }));
                Task.WaitAll(tasks.ToArray());
            }
            Console.WriteLine("Tickets has been sold out. Press any key to quit:");
        }
        //卖票方法
        public static void SellTicket(string windowName, object obj) 
        {
            string nameOfWindow = windowName;
            Ticket ticket = obj as Ticket;
            lock (ticket)
            {
                if (ticket.NumOfTickets > 0)
                {
                    try
                    {
                        ticket.NumOfTickets--;
                        Console.WriteLine(DateTime.Now.ToString() + ":" + nameOfWindow + " sells a ticket, " + ticket.NumOfTickets + " tickets left.");
                    }
                    catch (Exception ex)
                    {
                        WriteLog(ex);
                    }
                }
                Random random = new Random();
                Thread.Sleep(random.Next(100,500));
            }
        }
        //打log方法
        private static void WriteLog(Exception ex)
        {
            string logUrl = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) + "\\SellTicketslog.txt";
            if (File.Exists(@logUrl))
            {
                using (FileStream fs = new FileStream(logUrl, FileMode.Append))
                {
                    using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
                    {
                        try
                        {
                            sw.Write(ex);
                        }
                        catch (Exception ex1)
                        {
                            WriteLog(ex1);
                        }
                        finally
                        {
                            sw.Close();
                            fs.Close();
                        }
                    }
                }
            }
            else
            {
                using (FileStream fs = new FileStream(logUrl, FileMode.CreateNew))
                {
                    using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
                    {
                        try
                        {
                            sw.Write(ex);
                        }
                        catch (Exception ex1)
                        {
                            WriteLog(ex1);
                        }
                        finally
                        {
                            sw.Close();
                            fs.Close();
                        }
                    }
                }
            }
        }
    }
    //票类
    class Ticket 
    {
        public int NumOfTickets { get; set; }
        public Ticket(int num) 
        {
            this.NumOfTickets = num;
        }
    }
}

本次修改了售罄方法和入口方法（橙色字体），运行结果如下：

欢迎继续提出意见！谢谢大家~

码农公寓

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