Run mvn clean test to make sure you have JDK 8 and all dependencies in place.

Run J01_HelloWorldTest.java from your favourite IDE and make sure it compiles and passes.

If you see this error message during maven build:

[INFO] BUILD FAILURE
...
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project java8:
Fatal error compiling: invalid target release: 1.8 -> [Help 1]

it means you are not compiling using Java 8. Download JDK 8 and let maven use it:

$ export JAVA_HOME=/path/to/jdk8

This project is released under version 2.0 of the Apache License.