死锁的例子

/**
 * Description:
 * <br/>Copyright (C), 2008-2010, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee [e-mail]
 * @version  1.0
 */
class A
{
    public synchronized void foo( B b )
	{
		System.out.println("当前线程名: " + 
			Thread.currentThread().getName() + " 进入了A实例的foo方法" );
		try
		{
			Thread.sleep(200);
		}
		catch (InterruptedException ex)
		{
			ex.printStackTrace();
		}
		System.out.println("当前线程名: " + 
		Thread.currentThread().getName() + " 企图调用B实例的last方法");
		b.last();
	}

	public synchronized void last()
	{
		System.out.println("进入了A类的last方法内部");
	}
}

class B
{
	public synchronized void bar( A a )
	{
		System.out.println("当前线程名: "
			+ Thread.currentThread().getName() + " 进入了B实例的bar方法" );
		try
		{
			Thread.sleep(200);
		}
		catch (InterruptedException ex)
		{
			ex.printStackTrace();
		}
		System.out.println("当前线程名: " 
		+ Thread.currentThread().getName() + " 企图调用A实例的last方法");
		a.last();
	}

	public synchronized void last()
	{
		System.out.println("进入了B类的last方法内部");
	}
}

public class DeadLock implements Runnable
{
	A a = new A();
	B b = new B();

	public void init()
	{
		Thread.currentThread().setName("主线程");
		//调用a对象的foo方法
		a.foo(b);
		System.out.println("进入了主线程之后");
	}
	public void run()
	{
		Thread.currentThread().setName("副线程");
		//调用b对象的bar方法
		b.bar(a);
		System.out.println("进入了副线程之后");
	}
	public static void main(String[] args)
	{
		DeadLock dl = new DeadLock();
		//以dl为target启动新线程
		new Thread(dl).start();
		//执行init方法作为新线程
		dl.init();
	}
}

主线程保持着A对象的锁，等待B对象的锁。子线程保持着B对象的锁，等待A对象的锁。2个线程互相等待对方释放锁，造成死锁。