抽象类

public abstract class Animal {
public abstract void cry();
public abstract String getAnimalName();

}

public class Simulator {
public void playSound(Animal animal){
System.out.println("现在模拟器模拟"+animal.getAnimalName()+"的叫声:");
animal.cry();
}
}

public class Dog extends Animal{
public void cry() {
System.out.println("汪汪...");
}
public String getAnimalName() {
return "狗狗";
}
}

public class Cat extends Animal {

public void cry() {
System.out.println("喵喵...");
}
public String getAnimalName() {
return "猫猫";
}
}

public class Application {

public static void main(String args[]) {
Simulator simulator=new Simulator();
simulator.playSound(new Dog());
simulator.playSound(new Cat());
}
}

总结：对于测试类中的 simulator.playSound(new Dog());这一句，我不明白其含义，动物类为Dog类的父类，为上转型对象的话，怎么没有相应语句...