英文:
How to access the object state from interface reference in JAVA
问题
我想知道在JAVA中是否提供了灵活性，以访问使用接口引用封装的对象的状态。我正在使用Guava缓存设计缓存库。Guava缓存是通用的。在我的库中，我想使用接口实例化这个通用库，以某种通用类型实例化，如下所示。
LoadingCache<CacheKey, CacheValue> cache;
其中CacheKey和CacheValue是接口。
public interface CacheKey {
CacheValue calculateValue();
}
public interface CacheValue {
}
我成功地能够使用此缓存来存储实现这些接口的类型对。
但是我面临的问题是，当我使用以下方式从缓存中检索值时：
cache.get(key);
它会返回一个带有实际对象的CacheValue引用。我需要对实际对象类型进行静态转换，以访问底层对象的状态，如下所示。
AccountID aid = (AccountID) cache.get(key);
是否有任何方法可以避免这种静态转换，并在不进行类型转换的情况下访问底层对象的状态？
更新
我正在我的库中实例化Guava缓存，以支持任何键类型和值类型，不仅限于AccountID。因为我正在实例化缓存，所以它应该具有具体的类型，而不是像CacheKey<T>这样的通用类型。
英文:
I want t know is there any flexibility provided in JAVA to access the state of the object wrapped with interface reference. I am designing a cache library using guava cache. Guava cache is a generic. In my library I want to instantiate this Generic library with some generic type using the interfaces. as below.
LoadingCache<CacheKey, CacheValue> cache;
where CacheKey and CacheValue are interfaces.
public interface CacheKey {
CacheValue calculateValue();
}
public interface CacheValue {
}
I am successfully able to use this cache for storing the type pairs that implement these interfaces.
But the problem I am facing is When I retrieve the values from the cache using
cache.get(key);
It returns me CacheValue reference with actual object wrapped inside it. I need to do static cast to the actual object type to access the underlying object's state like below.
AccountID aid = (AccountID)cache.get(key);
Is there any way I can avoid this static casting and access the underlying object's state without typecasting?
UPDATE
I am instantiating the guava cache in my library to support any key type and value type not only AccountID. As I am instantiating the cache it should have the concrete types. not generic like CacheKey<T>
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