多态是编译时行为还是运行时行为？
答：运行时行为。可利用random随机数随机生成对象，在运行时产生对象，来证明多态试运行时行为。
代码：
import java.util.Random;
class Animal {
String name = "animal";
public String getinfo() {
return null;
}
}
class Cat extends Animal {
String name = "cat";
int age = 3;
public String getinfo() {
return String.format("name: %s age: %d", name, age);
}
}
class Dog extends Animal {
String name = "dog";
int age = 5;
public String getinfo() {
return String.format("name: %s age: %d", name, age);
}
}
public class PolymorphicDemo {
public static void main(String[] args) {
// TODO Auto-generated method stub
PolymorphicDemo pd = new PolymorphicDemo();
Animal a = pd.getInstance(new Random().nextInt(3));
System.out.println(a.getinfo());
}
public Animal getInstance(int key) {
switch (key) {
case 0:
return new Cat();
case 1:
return new Dog();
default:
return new Animal();
}
}
}
输出：
name: cat age: 3
