java为什么实例变量不调用方法不重写升级？

Question

我有母类动物和子类狗

public class Animal {
public void bark() {
    System.out.println("sua");
}

}

及

public class Dog extends Animal {
public void bark() {
    System.out.println("Go go");
}
public void eat(){
    System.out.println("an com");
}

}

还有班长

public class MainDemo {

public static void main(String[] args) {
    Animal animal = new Dog();
    animal.bark();
    animal.eat();
}

}

为什么实例动物在多态运行时不调用方法eat

Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method eat() is undefined for the type Animal

at tinhdahinh.MainDemo.main(MainDemo.java:8)