Java编码风格，局部变量vs重复的方法调用 [英] Java coding style, local variables vs repeated method calls

问题描述

我喜欢使用局部变量而不是多次调用同一个方法。

  / * 
 *我更喜欢这个
 * / 
车辆= person.getVehicle （）
 if（vehicle instanceof Car）{
 Car car =（Car）vehicle; 
 car.openSunroof（）; 
} else if（vehicle instanceof Bike）{
 Bike bike =（Bike）vehicle; 
 bike.foldKickstand（）; 
} 
 / * 
 *而不是
 * / 
 if（person.getVehicle（）instanceof Car）{
 Car car = person.getVehicle（）; 
 car.openSunroof（）; 
} else if（person.getVehicle（）instanceof Bike）{
 Bike bike =（Bike）person.getVehicle（）; 
 bike.foldKickstand（）; 
} 
  

• 我相信第一种方法是


• 我认为第二种方式违反了DRY原则


• 我发现第一种方式更易读，更容易调试。




解决方案

是的，第一个是绝对更好。我永远不会去第二种方法。
但是你应该考虑更多地使用多态性。依靠 instanceof 这么重的是不好的OO设计。




I prefer to use local variables rather than multiple calls to the same method.

/*
 * I prefer this
 */
Vehicle vehicle = person.getVehicle()
if (vehicle instanceof Car) {
   Car car = (Car) vehicle;
   car.openSunroof();
} else if (vehicle instanceof Bike) {
   Bike bike = (Bike) vehicle;
   bike.foldKickstand();
}
/*
 * Rather than this
 */
if (person.getVehicle() instanceof Car) {
   Car car = (Car) person.getVehicle();
   car.openSunroof();
} else if (person.getVehicle() instanceof Bike) {
   Bike bike = (Bike) person.getVehicle();
   bike.foldKickstand();
}

• I believe that the first way is going to perform a tiny bit faster
• I think the second way violates the DRY principle
• I find the first way more readable and easier to debug (... OK negligible because I could step over)
• I don't want to have to deal with the possibility of changed object state

Which do you prefer and why?

解决方案

Yeah the first one is definitely better. I would never go for the second method. But you should think of using polymorphism more. Relying on instanceof so heavyly is not good OO design.

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