[英]Kotlin lambda / Java SAM interop - type mismatch
I have an existing Java interface defined as follows 我有一个现有的Java接口定义如下
public interface MyRetriever extends Function<String, Optional<String>> {}
and want to define a variable holding a Kotlin lambda which conforms to the SAM conversion as per my understanding 并且想根据我的理解定义一个持有Kotlin lambda的变量,该变量符合SAM转换
var a : MyRetriever = { s : String -> Optional.ofNullable(s.toLowerCase()) }
But instead I get a type mismatch error. 但相反,我得到了类型不匹配错误。
Type missmatch.
Required: MyRetriever
Found: (String) -> Optional<String>
The lambda actually matches the Java function definition, what am I missing here? lambda实际上匹配Java函数定义,我在这里缺少什么?
When doing a SAM conversion, you need to explicitly provide a type: 进行SAM转换时,您需要明确提供类型:
var a = MyRetriever { s : String -> Optional.ofNullable(s.toLowerCase()) }
Note that you may omit declaration of type for a
the way you did it before. 需要注意的是,你可以省略类型声明a
你以前做过的方式。
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