OpenJDK 7 is an open source implementation of version 7 of the Java Development Kit, Standard Edition. It includes tools for developing, testing, and running programs written in Java. apache-ant is a required dependency and you have to install it before you build openjdk. However, you do not need to install Oracle's jdk, since it's only a runtime dependency of apache-ant. Before installing this package please consider any other jdk's/jre's that you have already installed as they may cause conflicts with the PATH, JAVA_HOME and MANPATH variables. After installing the package you will need to logout/reboot your machine as it will add new files to the /etc/profile.d folder. This script may take a couple of hours to complete and will require about 11 GB of disk space for its temporary directory. It defaults to "/tmp/SBo" and you may redefine it like this: TMP=/your/temporary/dir ./openjdk.SlackBuild The 'cacerts' binary is a keystore containing CA certificates which are used by Java applications. It is taken from the CentOS package 'ca-certificates-2015.2.4-65.0.1.el6_6.noarch.rpm'. If you get an error like Internal compiler error: java.lang.NullPointerException at org.eclipse.jdt.internal.compiler.ReadManager.run(ReadManager.java:166) simply run the build again. This happens early so it shouldn't be that of a problem. At least 1 out of 5 runs so far have always succeded.