java - 子类中的方法参数与 getter

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关闭。这个问题是 opinion-based 。目前不接受答案。

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已关闭 9 年前。

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我们在办公室进行了讨论，但双方都没有被说服。假设我们有

enum Food {
    CHICKEN, HAMBURGER, FISH;
}

我们需要 Dog 的多个实现，它们需要回答它们是否快乐，这取决于它们是否喜欢给它们的食物或者其他东西。它需要非常灵活。哪个更好:答:

abstract class Dog {
    //not sure if this can be abstract in reality, but does it matter?
    abstract Set<Food> getFavoriteFoods();

    boolean isFoodOk(){
        return getFavoriteFoods().contains(Food.CHICKEN);
    }

    //in reality sometimes more conditions are needed here...
    boolean isHappy(){
        return isFoodOk();
    }
}



public class BullDog extends Dog {
    static final Set<Food> FAVORITE_FOODS = new HashSet<Food>();
    static {
        FAVORITE_FOODS.add(Food.CHICKEN);
        FAVORITE_FOODS.add(Food.FISH);
    }

    Set<Food> getFavoriteFoods(){
        return FAVORITE_FOODS;
    }
}

或B:

abstract class Dog {
    abstract boolean isHappy();

    boolean isFoodOk(Set<Food> f){
        return f.contains(Food.CHICKEN);
    }
}

public class BullDog extends Dog {
    static final Set<Food> FAVORITE_FOODS = new HashSet<Food>();
    static {
        FAVORITE_FOODS.add(Food.CHICKEN);
        FAVORITE_FOODS.add(Food.FISH);
    }

    @Override
    boolean isHappy() {
        return isFoodOk(FAVORITE_FOODS);
    }
}

如果答案是 A，我会有另一个问题。

注意:我编辑了代码，因为那里有一个愚蠢的错误 - 当然 FAVORITE_FOODS 应该在 BullDog 中声明，而不是 Dog。但这并不能回答问题。

Answer 1

我会说没有，因为在所有方法中 Set<Food>标记为static final因此，同一个集合将在 Dog 的所有实例之间共享。类(class)。另外，通过声明 Set如static final并不意味着其内容不能被修改，所以实际上 Dog 的任何客户端类或任何子类可能会添加新的食物，甚至清除它和所有 Dog s将会受到影响。

这种方法可以做到:

public abstract class Dog {
    //this field should be final only so the variable cannot be modified
    protected final Set<Food> favoriteFood;

    protected Dog(Food ... food) {
        //now the Set cannot be modified as well
        favoriteFood = Collections.unmodifiableSet(new HashSet<Food>(Arrays.asList(food)));
    }

    //no need to be abstract, and clients cannot modify this set
    public Set<Food> getFavoriteFoods() {
        //I would recommend returning a new set that 
        return favoriteFood;
    }

    //You need to check if the dog likes the food to see if its ok
    public boolean isFoodOk(Food food){
        //not sure if your requirement is that it always should compare with CHICKEN, really odd...
        return getFavoriteFoods().contains(food); //Food.CHICKEN);
    }

    //IMO this method needs a complete redesign, since I don't know the details I can't provide a solution =\
    //at most it can be an abstract method and let each dog subclass implement it
    public abstract boolean isHappy();
    //boolean isHappy(){
    //    return isFoodOk();
    //}
}

public class BullDog extends Dog {
    public BullDog() {
        super(Food.CHICKEN, Food.FISH);
    }
    @Override
    public boolean isHappy() {
        //define how the bulldog is happy
        return ...;
    }
}