是否可以投射Map< Field，Value>到映射<镜像，镜像>当知道Field和Value扩展镜像？ [英] Is it possible to cast Map<Field, Value> to Map<Mirror, Mirror> when it is known that Field and Value extend Mirror?

问题描述

我试图向上投射地图< Field，Value> 到映射< Mirror，Mirror> 。
这对于转换是有意义的，因为 Field和Value extends Mirror ，但是我得到一个无法转换错误

是否不可能投放双重类型的地图？

谢谢您，

p>

Dean

解决方案

我认为只有当您定义

 地图< Field，Value& 
  

为

 地图< ;?扩展镜像，？ extends Mirror> 
  

但是否则就不一样了。

I am trying to cast upwards Map<Field, Value> to Map<Mirror, Mirror>. It makes sense for the cast to work, as both Field and Value extend Mirror, however I am getting a "cannot cast" error.

Is it simply not possible to cast Maps with double types? If so, how else can I cast?

I would appreciate any help!

Thank you,

Dean

解决方案

I think that would be possible only if you define the

Map<Field, Value> 

as

Map<? extends Mirror, ? extends Mirror>

But otherwise, it's not the same thing.

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