Thanks @JordiCP - Indeed, I also have Java7 installed although it is not in my path. I now already changed the Lamda expressions into Anonymous classes but I will check next time.
I missed that one. Maybe this is still the case? If yes, maybe one day Erel will make the B4X enviroment compatible with Lamdas? I like Lamda.
Anyway, I found out that in Android Studio, you can simple highlight the "->" sign and then type ALT + ENTER and you get an option to automatically convert Lamda into an Anonymous class.
Reading this page, there is an overview of supported Java 8 Language Features and APIs.
This made be believe that, at least Lamda Epression were compatible by any minSdkVersion...
Anyway, it's not a big deal. You have fantastic products and support and this is what counts