1 //接口與具體的實現類之間也存在多態性 2 public class TestInterface { 3      4     public static void main(String[] args) { 5         Duck d = new Duck(); 6         TestInterface.test1(d); 7         TestInterface.test2(d); 8         TestInterface.test3(d); 9     }10     11     public static void test1(Runner r){//Runner r = new Duck();12         r.run();//虛擬方法調用13     }14     public static void test2(Swimmer s){//Swimmer s = new Duck();15         s.swim();16     }17     public static void test3(Flier f){//Flier f = new Duck();18         f.fly();19     }20 }21 22 interface Runner{23     public abstract void run();24 }25 interface Swimmer{26     void swim();27 }28 interface Flier{29     void fly();30 }31 32 class Duck implements Runner,Swimmer,Flier{33 34     @Override35     public void fly() {36         System.out.