The Ginger Mumbly

I'm refreshing my Java knowledge at the moment and a friend is helping me go over all the nitty gritty stuff so that I can sit the SCJP exam. The first thing that he asked me to learn is a table that goes like this:

I know it's quite a simple table, but it is an ordered graph and I used some of the memory palace techniques that I've just read about in a Dominic O'Brien book to remember it. Now it's stuck in my head. Why did nobody tell us about this when we were at school?