Java 为什么我们需要decorator模式中的抽象decorator类？

在

装饰器模式中

，如果

删除decorators继承并删除的抽象decorator类

使装饰器直接继承装饰对象的接口 输出是相同的

我的问题是，为什么还要添加额外的

抽象类来制作装饰器呢


例如：

标准
decorator模式的
Scala
源代码如下：

而遵循上述步骤的我的版本如下：
（通过删除抽象decorator类（
CoffeeDecorator
此处），并让decorator直接继承被装饰者（
Coffee
此处））

在闲逛之后，我发现了区别。
抽象装饰器提供了默认的重写，因此在某些情况下，装饰器实现的类型更少，因为我们并不总是装饰所有的方法并提供公共的帮助程序

trait Coffee {
  def cost: Double
  def ingredients: String
}

class FreeMilk(decoratedCoffee: Coffee) extends Coffee {
  // this is a waste of line
  override def cost = decoratedCoffee.cost 
  override def ingredients = decoratedCoffee.ingredients + "," + "Milk"
}

abstract class CoffeeDecorator(decoratedCoffee: Coffee) extends Coffee {
  val sep = ", "
  override def cost = decoratedCoffee.cost
  override def ingredients = decoratedCoffee.ingredients
}
class FreeMilk2(decoratedCoffee: Coffee) extends CoffeeDecorator(decoratedCoffee) {
  // less typings and give you some base helpers
  override def ingredients = super.ingredients + sep + "Milk"
}

trait Coffee {
  def cost: Double
  def ingredients: String
}

class FreeMilk(decoratedCoffee: Coffee) extends Coffee {
  // this is a waste of line
  override def cost = decoratedCoffee.cost 
  override def ingredients = decoratedCoffee.ingredients + "," + "Milk"
}

abstract class CoffeeDecorator(decoratedCoffee: Coffee) extends Coffee {
  val sep = ", "
  override def cost = decoratedCoffee.cost
  override def ingredients = decoratedCoffee.ingredients
}
class FreeMilk2(decoratedCoffee: Coffee) extends CoffeeDecorator(decoratedCoffee) {
  // less typings and give you some base helpers
  override def ingredients = super.ingredients + sep + "Milk"
}