多態(tài)是編譯時(shí)行為還是運(yùn)行時(shí)行為？
答：運(yùn)行時(shí)行為?？衫胷andom隨機(jī)數(shù)隨機(jī)生成對(duì)象，在運(yùn)行時(shí)產(chǎn)生對(duì)象，來證明多態(tài)試運(yùn)行時(shí)行為。
代碼：

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();

        }
    }
}

輸出：

name: cat age: 3