Acme4J is a Java toolkit for obtaining automatically issued free TLS / SSL certificates from the Let's Encrypt Certificate Authority.
Java Map deep dive! Big round of updates. Notice especially the functional operations added in Java 8.
Java 8 comes with a set of built-in functional interfaces which can be used with e.g. the Streams API. This tutorial explains some of the core functional interfaces in Java.
You pretty much always have to set the Java compiler in your Maven POM files. Now the Maven tutorial explains how.