java通过继承来扩展接口

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()