Java 泛型扩展列表

Question

我有以下类(class):

public interface ServiceSynchronizableEntity {
    ....
}

public class BaseListResponse<T> {
    ....
}

public class BaseSynchronizableListResponse<T extends ServiceSynchronizableEntity> extends BaseListResponse<T> {
    ....
}

public class MySecondClass implements ServiceSynchronizableEntity {
    ....
}

public class MyFirstClass extends BaseSynchronizableListResponse<MySecondClass> {
    ....
}

public class What<S extends BaseSynchronizableListResponse<ServiceSynchronizableEntity>> {

}

然后我将其用作:

What what = new What<MyFirstClass>();

当我想使用MyFirstClass时作为扩展 BaseListResponse<ServiceSynchronizableEntity>> 的类型参数它向我展示了

Main.java:26: error: type argument MyFirstClass is not within bounds of type-variable S
    What what = new What<MyFirstClass>();
                         ^
where S is a type-variable: S extends BaseSynchronizableListResponse<ServiceSynchronizableEntity> declared in class What

出了什么问题？

编辑:缺少一门课。看:http://ideone.com/D4snKP

谢谢!

Answer 1

我之前发布的解决方案(现已删除)的类似之处在于它需要更改通用签名。

重要的变化来自:

class What<S extends BaseSynchronizableListResponse<ServiceSynchronizableEntity>> {}

至:

class What<S extends BaseSynchronizableListResponse<? extends ServiceSynchronizableEntity>> {}

参见http://ideone.com/wyXvcl对于固定版本