编程|多线程
看一下以下两个例子的运行结果：
//TestThread.cs
using System;using System.Threading;public class Test{ static int count=0; static void Main() { ThreadStart job = new ThreadStart(ThreadJob); Thread thread = new Thread(job); thread.Start(); for (int i=0; i < 5; i++) { count++; } thread.Join(); Console.WriteLine ("Final count: {0}", count); } static void ThreadJob() { for (int i=0; i < 5; i++) { count++; } }}
//InnerDataThread.cs
using System;using System.Threading;public class Test{ static int count=0; static void Main() { ThreadStart job = new ThreadStart(ThreadJob); Thread thread = new Thread(job); thread.Start(); for (int i=0; i < 5; i++) { int tmp = count; Console.WriteLine ("Read count={0}", tmp); Thread.Sleep(50); tmp++; Console.WriteLine ("Incremented tmp to {0}", tmp); Thread.Sleep(20); count = tmp; Console.WriteLine ("Written count={0}", tmp); Thread.Sleep(30); } thread.Join(); Console.WriteLine ("Final count: {0}", count); } static void ThreadJob() { for (int i=0; i < 5; i++) { int tmp = count; Console.WriteLine ("\t\t\t\tRead count={0}", tmp); Thread.Sleep(20); tmp++; Console.WriteLine ("\t\t\t\tIncremented tmp to {0}", tmp); Thread.Sleep(10); count = tmp; Console.WriteLine ("\t\t\t\tWritten count={0}", tmp); Thread.Sleep(40); } }}
Read count=0 Read count=0 Incremented tmp to 1 Written count=1Incremented tmp to 1Written count=1 Read count=1 Incremented tmp to 2Read count=1 Written count=2 Read count=2Incremented tmp to 2 Incremented tmp to 3Written count=2 Written count=3Read count=3 Read count=3Incremented tmp to 4 Incremented tmp to 4 Written count=4Written count=4 Read count=4Read count=4 Incremented tmp to 5 Written count=5Incremented tmp to 5Written count=5Read count=5Incremented tmp to 6Written count=6Final count: 6 |
再比较下面这个例子：
//使用Monitor.Enter/Exit
//MonitorThread.cs
using System;
using System.Threading;
public class Test
{
static int count=0;
static readonly object countLock = new object();
static void Main()
{
ThreadStart job = new ThreadStart(ThreadJob);
Thread thread = new Thread(job);
thread.Start();
for (int i=0; i < 5; i++)
{
Monitor.Enter(countLock);
int tmp = count;
Console.WriteLine ("Read count={0}", tmp);
Thread.Sleep(50);
tmp++;
Console.WriteLine ("Incremented tmp to {0}", tmp);
Thread.Sleep(20);
count = tmp;
Console.WriteLine ("Written count={0}", tmp);
Monitor.Exit(countLock);
Thread.Sleep(30);
}
thread.Join();
Console.WriteLine ("Final count: {0}", count);
}
static void ThreadJob()
{
for (int i=0; i < 5; i++)
{
Monitor.Enter(countLock);
int tmp = count;
Console.WriteLine ("\t\t\t\tRead count={0}", tmp);
Thread.Sleep(20);
tmp++;
Console.WriteLine ("\t\t\t\tIncremented tmp to {0}", tmp);
Thread.Sleep(10);
count = tmp;
Console.WriteLine ("\t\t\t\tWritten count={0}", tmp);
Monitor.Exit(countLock);
Thread.Sleep(40);
}
}
}
结果与上例InnerDataThread.cs是不一样的，原因就在于Monitor的使用了。
Read count=0Incremented tmp to 1Written count=1 Read count=1 Incremented tmp to 2 Written count=2Read count=2Incremented tmp to 3Written count=3 Read count=3 Incremented tmp to 4 Written count=4Read count=4Incremented tmp to 5Written count=5 Read count=5 Incremented tmp to 6 Written count=6Read count=6Incremented tmp to 7Written count=7 Read count=7 Incremented tmp to 8 Written count=8Read count=8Incremented tmp to 9Written count=9 Read count=9 Incremented tmp to 10 Written count=10Final count: 10 |
下面使用lock来锁定线程：
// LockThread.cs
using System;
using System.Threading;
public class Test
{
static int count=0;
static readonly object countLock = new object();
static void Main()
{
ThreadStart job = new ThreadStart(ThreadJob);
Thread thread = new Thread(job);
thread.Start();
for (int i=0; i < 5; i++)
{
lock (countLock)
{
int tmp = count;
Console.WriteLine ("Read count={0}", tmp);
Thread.Sleep(50);
tmp++;
Console.WriteLine ("Incremented tmp to {0}", tmp);
Thread.Sleep(20);
count = tmp;
Console.WriteLine ("Written count={0}", tmp);
}
Thread.Sleep(30);
}
thread.Join();
Console.WriteLine ("Final count: {0}", count);
}
static void ThreadJob()
{
for (int i=0; i < 5; i++)
{
lock (countLock)
{
int tmp = count;
Console.WriteLine ("\t\t\t\tRead count={0}", tmp);
Thread.Sleep(20);
tmp++;
Console.WriteLine ("\t\t\t\tIncremented tmp to {0}", tmp);
if (count < 100)
throw new Exception();
Thread.Sleep(10);
count = tmp;
Console.WriteLine ("\t\t\t\tWritten count={0}", tmp);
}
Thread.Sleep(40);
}
}
}
结果如何？与MonitorThread.cs比较一下，再想想看。
