父类的向上转型就是父类引用指向子类对象

 

public abstract class Animal {

    public abstract void eat();

}

 

public class Cat extends Animal {

    @Override
    public void eat() {
        System.out.println("cat eat fish");
    }
}

 

public class DemoMain {
    public static void main(String[] args) {
      // 编译看左，运行看右，父类引用指向子类对象就是向上转型
        Animal an = new Cat();
        an.eat();
    }
}