Comment 2 for bug 342097

Ubuntu is unable to package Sun Java's actual documentation files due to licensing restrictions, and thus uses an installer package which, during install, provides instructions on where to get the documentation. The error in your log reflects this:

"This package is an installer package, it does not actually contain the
 JDK documentation. You will need to go download one of the
 archives:

    jdk-6-doc.zip jdk-6-doc-ja.zip

(choose the non-update version if this is the first installation).

Please visit

    http://java.sun.com/javase/downloads/

now and download. The file should be owned by root.root and be copied
 to /tmp."

Please follow these instructions, then install sub-java6-doc again. I am marking this report as invalid, as this package is working as intended.