Set the environment variables JAVA8_HOME and JAVA7_HOME (optionally also
JAVA6_HOME and JAVA5_HOME) point to the installation directories of those
particular JDK versions.
Compile the project with Maven using the command:
mvn clean verify
To run the tests using Java 6 and Java 5, use the commands:
mvn clean verify -P java6
mvn clean verify -P java5
Finally copy the executable JAR from the retrolambda/target/ directory.