"设置"特定枚举类型但具有泛型

Question

假设我有一个抽象类

public abstract class Trainer<T extends Animal>{}

我有特定的培训师,如:

public DogTrainer extends Trainer<Dog>{}
public HorseTrainer extends Trainer<Horse>{}

这些"训练师"中的每一个都有一套固定的技巧,他们可以训练动物去做,我想使用Enums.所以我有一个界面:

public interface TrainingActions<T extends Animal>{}

在每个培训师中,我都有一个实现此界面的Enum.所以:

public DogTrainer extends Trainer<Dog>{
  public enum Trainables implements TrainingActions<Dog>{
    BARK, BITE, ROLLOVER, FETCH;
  }
}

public HorseTrainer extends Trainer<Horse>{
  public enum Trainables implements TrainingActions<Horse>{
    JUMP, TROT, REARUP;
  }
}

现在在每个Trainer类中,我想要一个方法说'trainingComplete',它将一个Enums作为输入并将其保存到一个集合中.所以

public DogTrainer extends Trainer<Dog>{
  public enum Trainables implements TrainingActions<Dog>{
    BARK, BITE, ROLLOVER, FETCH;
  }
  public Set<Trainables> completed = new HashSet<Trainables>();
  public void trainingComplete(Trainables t){completed.add(t);}
}

但是,我不想在每个培训师中定义每个特定培训师中的"已完成"集和"培训完成"方法,而是希望父母"培训师"课程中的某些内容可以强制执行Enum类型...所以它是Enums和泛型的奇怪组合.

这可能吗？

Answer 1

要指定接口的绑定并且它是枚举,您需要一个通用交集,如下所示:

class MyClass<T extends Enum<T> & SomeInterface> {}

请注意,当与类和接口相交时,该类必须出现在接口之前.

在这种情况下,你想要的仿制功夫是一个更复杂的级别,因为TrainingActions枚举的界面本身必须参考动物类型.

class Trainer<A extends Animal, T extends Enum<T> & TrainingActions<A>> {}

一个完整的工作示例,基于您发布的代码,编译是:

public class Animal {}

public interface TrainingActions<T extends Animal> {}

/**
 * A trainer that can teach an animal a suitable set of tricks
 * @param <A> The type of Animal
 * @param <T> The enum of TrainingActions that can be taught to the specified Animal
 */
public abstract class Trainer<A extends Animal, T extends Enum<T> & TrainingActions<A>> {
    private Set<T> completed = new HashSet<T>();
    public void trainingComplete(T t) {
        completed.add(t);
    }
}

public class Dog extends Animal {};

public class DogTrainer extends Trainer<Dog, DogTrainer.Trainables> {
    public enum Trainables implements TrainingActions<Dog> {
        BARK, BITE, ROLLOVER, FETCH;
    }
}

但我会更进一步,TrainingActions在Animal它们适用的特定类中定义几个枚举:

public class Dog extends Animal {
    public enum BasicTrainables implements TrainingActions<Dog> {
        SIT, COME, STAY, HEEL;
    }
    public enum IntermediateTrainables implements TrainingActions<Dog> {
        BARK, BITE, ROLLOVER, FETCH;
    }
    public enum AdvacedTrainables implements TrainingActions<Dog> {
        SNIFF_DRUGS, FIND_PERSON, ATTACK, GUARD;
    }
};

public class PuppyTrainer extends Trainer<Dog, Dog.BasicTrainables> {}

public class ObedienceTrainer extends Trainer<Dog, Dog.IntermediateTrainables> {}

public class PoliceTrainer extends Trainer<Dog, Dog.AdvacedTrainables> {}