lock关键字可以用来确保代码块完成运行，而不会被其他线程中断。这是通过在代码块运行期间为给定对象获取互斥锁来实现的。
首先定义Account类,如下所示:
public class Account
{
private int balance = 500;
public void WithDraw(int amount)
{
if (balance - amount > 0)
{
Console.WriteLine("{1}:before drawing:balance:{0},amount:{2}", balance, Thread.CurrentThread.Name, amount);
Thread.Sleep(500);
balance -= amount;
Console.WriteLine("{1}:after drawing:balance:{0},amount:{2}", balance, Thread.CurrentThread.Name, amount);
Console.WriteLine();
}
else
{
Console.WriteLine("{0}:no money", Thread.CurrentThread.Name);
Thread.CurrentThread.Abort();
}
}
public void DoTrans()
{
Random ran = new Random();
for (int i = 0; i < 10; i++)
{
WithDraw(ran.Next(50, 100));
}
}
}
该类中定义了某个帐户初使金额是500元,WithDraw方法用于从帐户中取钱,并在取钱之前判断要取的金额是否大于余额,在判断后如果满足条件则执行减操作,此处使用Thread.Sleep方法模拟操作过程中一些耗时操作以允许其他线程有机会执行.
DoTrans方法用于分10次随机从帐户中取款.接下来定义Main方法使用两个线程取款:
static void Main(string[] args)
{
Account a1 = new Account();
Thread t1 = new Thread(new ThreadStart(a1.DoTrans));
Thread t2 = new Thread(new ThreadStart(a1.DoTrans));
t1.Name = "Thread 11111";
t2.Name = "Thread 22222";
t1.Start();
t2.Start();
Console.ReadLine();
}
因此解决方法可以使用lock关键字,将Account的WithDraw方法修正如下:
public void WithDraw(int amount)
{
lock (this)
{
if (balance - amount > 0)
{
Console.WriteLine("{1}:before drawing:balance:{0},amount:{2}", balance, Thread.CurrentThread.Name, amount);
Thread.Sleep(500);
balance -= amount;
Console.WriteLine("{1}:after drawing:balance:{0},amount:{2}", balance, Thread.CurrentThread.Name, amount);
Console.WriteLine();
}
else
{
Console.WriteLine("{0}:no money", Thread.CurrentThread.Name);
Thread.CurrentThread.Abort();
}
}
}
