public class Test
{
	// 测试
	public static void main(String[] args) throws Exception
	{
		Object obj = new Object();
		// 启动两个线程
		Thread1 t1 = new Thread1(obj);

		Thread2 t2 = new Thread2(obj);

		t1.start();
		t2.start();
	}

}

// 一个线程打印1-52
class Thread1 extends Thread
{
	private Object obj;

	public Thread1(Object obj)
	{
		this.obj = obj;
	}

	public void run()
	{
		synchronized (obj)
		{
			// 打印1-52
			for (int i = 1; i < 53; i++)
			{
				System.out.print(i + " ");
				if (i % 2 == 0)
				{
					// 不能忘了 唤醒其它线程
					obj.notifyAll();
					try
					{
						obj.wait();
					}
					catch (InterruptedException e)
					{
						e.printStackTrace();
					}
				}
			}
		}

	}

}

// 另一个线程打印字母A-Z
class Thread2 extends Thread
{
	private Object obj;

	public Thread2(Object obj)
	{
		this.obj = obj;
	}

	public void run()
	{
		synchronized (obj)
		{
			// 打印A-Z
			for (int i = 0; i < 26; i++)
			{
				System.out.print((char) ('A' + i) + " ");
				// 不能忘了 唤醒其它线程
				obj.notifyAll();
				try
				{
					// 最后一个就不要等了
					if (i != 25)
					{
						obj.wait();
					}
				}
				catch (InterruptedException e)
				{
					e.printStackTrace();
				}

			}

		}
	}

}

线程交替有序执行任务