The recent 1.3.2 release raised target Java version from 8 to 11. However, some project I'm working on is still on Java 8, and I believe many existing projects out there are not ready to upgrade to 11 yet.

I find that the only place where Java 11 features were used was in the tests. This PR replaces them with Java 8 compatible implementation and reverts minimum required Java version to 8. Please consider staying compatible with Java 8 for a bit longer!