マルチステートの例

class MainBoard
{
	public void run()
	{
		System.out.println("MainBoard run");
	}
	public void usePCI(PCI p)  //PCI p=new NetCard()//              ，        。
	{
		if(p!=null)
		{
			p.open();
			p.close();
		}
		else
		{
			System.out.println("      ");
		}
	}
}
interface PCI
{
	public void open();
	public void close();
}

class NetCard implements PCI
{
	public void open()
	{
		System.out.println("NetCard open");
	}
	public void close()
	{
		System.out.println("NetCard close");
	}
}

class SoundCard implements PCI
{
	public void open()
	{
		System.out.println("SoundCard open");
	}
	public void close()
	{
		System.out.println("SoundCard close");
	}
}
class DuoTaiDemo3
{
	public static void main(String args[])
	{
		MainBoard mb=new MainBoard();
		mb.run();
		mb.usePCI(null);
		mb.usePCI(new NetCard());
		mb.usePCI(new SoundCard());
	}
}