super.bark(); 不要第一个括号
Write a concrete meow( ) method 抽象类实例化后要加一个实例化的方法。
抽象类里可以没有抽象方法。
What does it mean to say that inheritance hierarchies are coupled? Changes to the parent affect the child 父类的变化会影响子类
不对因为父类里没有constructor,必须要有
public class Snake {
public int length;
public Snake(int length) { this.length = length;}
}
-------------------------------
public class Boa extends Snake {
public Boa( ) { this.length = 0;}
}