abstract class Animal
{
public abstract void eat();
}
class Cat extends Animal
{
public void eat()
{
  System.out.println("猫吃鱼");
}
public void catchMouse()
{
  System.out.println("抓老鼠");
}
}
class Dog extends Animal
{
public void eat()
{
  System.out.println("吃骨头");
}
public void kanJia()
{
  System.out.println("看门");
}
}
class Pig extends Animal
{
public void eat()
{
  System.out.println("吃饲料");
}
public void gonDi()
{
  System.out.println("拱地");
}
}

class DuoTaiDemo1
{
public static void main(String[] args)
{

  function(new Cat());
  function(new Dog());
  function(new Pig());
}
public static void function(Animal a)//运用多态父类引用指向子
类对象
{
  if(a instanceof Cat)
  {
   Cat c=(Cat)a;//强制向下转型，只能转父类引用不
能转对象。
   c.catchMouse();
  }
  else if(a instanceof Dog)
  {
   Dog c=(Dog)a;
   c.kanJia();
  }
  else if(a instanceof Pig)
  {
   Pig c=(Pig)a;
   c.gonDi();
  }
}
}

abstract class Animal
{
public abstract void eat();
}
class Cat extends Animal
{
public void eat()
{
  System.out.println("猫吃鱼");
}
public void catchMouse()
{
  System.out.println("抓老鼠");
}
}
class Dog extends Animal
{
public void eat()
{
  System.out.println("吃骨头");
}
public void kanJia()
{
  System.out.println("看门");
}
}
class Pig extends Animal
{
public void eat()
{
  System.out.println("吃饲料");
}
public void gonDi()
{
  System.out.println("拱地");
}
}

class DuoTaiDemo1
{
public static void main(String[] args)
{

  function(new Cat());
  function(new Dog());
  function(new Pig());
}
public static void function(Animal a)//运用多态父类引用指向子
类对象
{
  if(a instanceof Cat)
  {
   Cat c=(Cat)a;//强制向下转型，只能转父类引用不
能转对象。
   c.catchMouse();
  }
  else if(a instanceof Dog)
  {
   Dog c=(Dog)a;
   c.kanJia();
  }
  else if(a instanceof Pig)
  {
   Pig c=(Pig)a;
   c.gonDi();
  }
}
}