动态绑定和静态绑定

class Drinks{
  public void drink(){
    System.out.println("not sure what it is");
  }

  public static void main(String []args){
    Drinks drink = DrinkFactory.getDrink();
    drink.drink();
  }
}

class DrinkFactory {
  public static Drinks getDrink() {
    return new Tea();
  }
}

class Tea extends Drinks{
//overriding the static method
  public void drink(){
    System.out.println("this is Tea");
  }
}

class Water extends Drinks{
//overriding the static method
  public void drink(){
    System.out.println("this is Water");
  }
}