如何从java中的两个不同类调用相同的方法

Question

I have two classes Apple and Orange like this:

public final  class Apple{
    int getJuice();
}
public final class Orange{
    int getJuice();
}

and I cannot change them . I have third class fruitsManeger like this:

class FruitManeger {
     Apple apple;
     Orange orange;

     enum Fruits{
        Apple,Orange
     }

     Fruits favorFruits;    

     int getJoice(){
         if(favorFruits==Fruits.Apple){
               apple.getJuice();
         }else if(favorFruits==Fruits.Orange){
               orange.getJuice();
         } 
     }

}

My Question: what is best way to implement getJuice method in FruitManeger class?.

as you can see if I have a lot of fruits I should add a lot of if else expiration.

of course, I can use reflection to call methods by name but it's not a good idea when getJuice method return an object and you want to do something same with that.

is there any better way?

Answer 1

is there any better way?

Yes, Refactor that application into a more oop way...

Remember: you cannot Modify Apple or Orange, but OOP allows you extending those classes for sure since they are not final...

class CorrectApple extends Apple implement IJuiceble{
    @Override
    int getJuice();
}
class CorrectOrange extends Orange  implement IJuiceble{
    @Override
    int getJuice();
}

now the

interface IJuiceble{
    int getJuice();
}

and finally the manager:

class FruitManeger {
     private CorrectApple apple;
     private CorrectOrange orange;

     int getJoice(IJuiceble correctfruit){
         return correctfruit.getJuice();
     }
}

Answer 2

You can use switch instead of if/else.

class FruitManager {
    Apple apple;
    Orange orange;

    enum Fruits {
        Apple, Orange
    }

    Fruits favorFruits;

    int getJoice() {
        switch (favorFruits) {
        case Apple:
            apple.getJuice();
            break;
        case Orange:
            orange.getJuice();
            break;

        default:
            System.err.println("Fruit not found. " + favorFruits);
        }
    }

Answer 3

By referring this Answer

interface IScalable {
   void setScale(int scale);
   int getScale();
}

class DataSizeAction extends EncoderAction implements IScalable {
   ...
}

class SomeoneElse {
   private int scale = 2;

   public void setScale(IScalable scalable) {
      scalable.setScale(this.scale);
   }
}