That used to be the case, but the build tools have supported lambdas for a while now, and it works even on very old devices. On the other hand, Java 8 classes

That used to be the case, but the build tools have supported lambdas for a while now, and it works even on very old devices. On the other hand, Java 8 classes like java.util.Stream only exist on API 24+ devices. So if you want to support older classes, you can't use the standard stream library.