You should always understand the programming language your platform of choice is built upon. That means Java if you are going to use the JVM in some way, just

You should always understand the programming language your platform of choice is built upon. That means Java if you are going to use the JVM in some way, just like it means C if you are going to develop native applications on Windows or Linux. I have always been astonished at VB6 programmers which ignored what a Variant was, when they were using such datatype all the time.