Java is actually quite easy to install under Slackware 14.0.
Check out the java/ directory in extra/. Download it locally on your machine, with all its content.
Then download the Java tarball from the Oracle site. Choose between JRE and JDK according to your needs. Be sure to download the right package for your architecture (32-bit or 64-bit). Put the downloaded jre-*.tar.gz or jdk-*.tar.gz file in your java/ directory.
Make sure java.SlackBuild is executable and run it as root:
The resulting jre-*.txz or jdk-*.txz package can be found in /tmp.
JRE and JDK can't be distributed as is anymore due to some licensing issues.