多态接口（电脑运行实例）

package BxdStudy;

/**
 * 电脑运行实例
 * 电脑运行基于主板
 * @author 董
 *
 */
public class DuoTaiInter {
	public static void main(String[] args) {
		MainBoard mainBoard = new MainBoard();
		mainBoard.usePCI(null);
		//接口型引用指向自己的子类对象
		mainBoard.usePCI(new NetCard());
		mainBoard.usePCI(new SoundCard());
	}
}

//主板类
class MainBoard
{
	public void run() {
		System.out.println("Main Board主板运行...");
	}
	
	//重点：PCI pci = new NetCard()或者PCI pci = new SoundCard()接口型引用指向自己的子类对象
	public void usePCI(PCI pci) {
		if(pci != null) {
			pci.open();
			pci.close();
		}
	}
}

//多态接口
interface PCI
{
	public void open();
	public void close();
}

//网卡类实现PCI
class NetCard implements PCI{

	@Override
	public void open() {
		System.out.println("netCard网卡打开了");
	}
	
	@Override
	public void close() {
		System.out.println("netCard网卡关闭了");
	}
	
}

//声卡实现PCI
class SoundCard implements PCI{

	@Override
	public void open() {
		System.out.println("soundCard声卡打开了");
	}

	@Override
	public void close() {
		System.out.println("soundCard声卡关闭了");
	}
	
}

运行结果;
netCard网卡打开了
netCard网卡关闭了
soundCard声卡打开了
soundCard声卡关闭了