java基础——小例子说明封装、继承、多态

一、继承关系:子类自动拥有父类非私有属性与方法(java只能单继承)

//继承
public class OOPTest2
{
     public static void main(String[] args)
     {
        Dog d = new Dog();
        System.out.println(d.age);
        d.play(); 
     }
}
class Animal
{
   protected int age=2;
   public void play()
   {
            
     System.out.println("animal is playing...");
            
   }
}
class Dog extends Animal
{
   //没有写子类的属性与方法
   //子类自动拥有父类非私有属性和方法
}

二、接口实现多态:同一个接口的不同实现

//多态
public class Test
{
     public static void main(String[] args)
     {
         //同一个接口的不同实现
         Pet snake =  new Snake();
         snake.play();
         Pet cat = new Cat();
         cat.play();
      
     }
}
//接口
interface Pet
{
   public void play();
}
class Snake implements Pet
{
   public void play()
   {
      System.out.println("Snake is playing.........");
   }
}
class Cat implements Pet
{
      public void play()
      {
         System.out.println("Cat is playing...........");
      }
}