小疑问,求答疑!
一个类A实现了接口B,那new A()为什么能当成接口B的对象?比如:
interface USB
{
public void start();
public void stop();
}
class Computer
{
public static void plugin(USB usb)
{
usb.start();
System.out.println("===USB is working!===");
usb.stop();
}
}
class Flash implements USB
{
public void start()
{
System.out.println("Flash start working!");
}
public void stop()
{
System.out.println("Flash stop working!");
}
}
public class drive
{
public static void main(String arga[])
{
Computer.plugin(new Flash());
}
}
new Flash()问什么能作为(USB usb)呢?