What does he want to make? This should be the primary deciding factor every time "what language should I learn" comes up. Java is particularly suitable for writing simple GUI applications and mobile apps. (Android or J2ME) Ruby seems to be more useful than Java if you're interested in writing web applications. Both are fine if he just wants to write command-line apps, but Java's speed will pay off if those command-line apps are doing serious number crunching.

Have him give Processing (http://processing.org/) a spin- Processing is 99% Java, but you can start writing loops, conditionals and functions without learning what a class is. It's very easy to work your way up from Processing to full-on Java.