如果一个方法的参数是接口类型，就可以将任何实现该接口类的实例的引用传递给该接口参数，那么接口参数就可以回调类实现的接口的方法。
interface SpeakHello
{
public void speakHello();
}
class china implements SpeakHello
{
public void speakHello()
{
System.out.println("china/n");
}
}
class english implements SpeakHello
{
public void speakHello()
{
System.out.println("english/n");
}
}
class KindHello
{
public void lookHello(SpeakHello hello)
{
hello.speakHello();
}
}
public class hello {
public static void main(String[] args) {
// TODO Auto-generated method stub
KindHello kh=new KindHello();
kh.lookHello(new china());
kh.lookHello(new english());
}
}
