接口主要是为了向上转型，从而使基类（接口方法）更具灵活性！不想废话，看例子：
/**
*
*/
package interfaces;interface Monster{
void menace();
}interface DangerousMonster extends Monster{
void destory();
}interface Lethal{
void kill();
}class DragonZilla implements DangerousMonster{
public void menace(){
System.out.println("DangerousMonster menace()");
}public void destory(){
System.out.println("DangerousMonster destory()");
}
}interface Vampire extends DangerousMonster,Lethal{
void drinkBlood();
}class VeryBadVampire implements Vampire{
public void menace(){
System.out.println("VeryBadVampire menace()");
}public void destory() {
// TODO Auto-generated method stub
System.out.println("VeryBadVampire destroy()");
}public void kill() {
// TODO Auto-generated method stub
System.out.println("VeryBadVampire kill()");
}public void drinkBlood() {
System.out.println("VeryBadVampire dinrkBlood()");}
}
public class HorrorShow {
static void u(Monster b){b.menace();}
static void v(DangerousMonster d){
d.menace();
d.destory();
}
static void w(Lethal l){
l.kill();
}
public static void main(String[] args) {
// TODO Auto-generated method stub
DangerousMonster barney = new DragonZilla();
u(barney);
v(barney);Vampire Vlad = new VeryBadVampire();
u(Vlad);
v(Vlad);
w(Vlad);
}}
结果
DangerousMonster menace()
DangerousMonster menace()
DangerousMonster destory()
VeryBadVampire menace()
VeryBadVampire menace()
VeryBadVampire destroy()
VeryBadVampire kill()
java通过继承来扩展接口