First, for Java developers only

As Android developers, there are many ways to write an app and get tired of seeing how the lack of features of the Java (Java6 by default) platform embedded in the Android SDK slows the coding process. Notice that Java6 last public update dates from 2013 and that is the version you are expected to use on Android development with Java. You can use Java8 language features but most of the powerful features can only be used in devices that are running Android 7.0 Nougat (API 24).

By May 7, 2019, Android 10 not released yet, there was a total close to 41.9% devices running Android OS prior Nougat out of 2.5 billion active devices.