暴露封装类方法的经验法则是什么

Question

请考虑以下类比:如果我们有一个类:"Car",我们可能会期望它有一个"Engine"实例.如:"汽车HAS-A发动机".类似地,在"引擎"类中,我们期望"启动系统"或"冷却系统"的实例各自具有其适当的子组件.

根据封装的性质,汽车"HAS-A""散热器软管"和发动机不是真的吗？

因此,做这样的事情是否合适:

public class Car {
   private Engine _engine;

   public Engine getEngine() {
      return _engine;
   }

   // is it ok to use 'convenience' methods of inner classes?
   // are the following 2 methods "wrong" from an OO point of view?
   public RadiatorHose getRadiatorHose() {
      return getCoolingSystem().getRadiatorHose();
   }

   public CoolingSystem getCoolingSystem() {
       return _engine.getCoolingSystem();
   }
}

public class Engine {
    private CoolingSystem _coolingSystem;

    public CoolingSystem getCoolingSystem() {
        return _coolingSystem;
    }
}

public class CoolingSystem {
    private RadiatorHose _radiatorHose;

    public RadiatorHose getRadiatorHose() {
        return _radiatorHose;
    }
}

public class RadiatorHose {//...
}

Answer 1

检查迪米特定律。