Hi Jeanne,
In my case, it comes from a history of working with Ben on a mixture of training and conference materials.
Way back before we were married, he talked me into creating an animation that showed the parallel generational garbage collector in action – so the first few
Java conferences I went to with him, I knew very little about Java in general, but could talk for hours about the nuances of garbage collection!
Over the years, we've developed a whole suite of illustrations, and alongside that a sort of visual language that works well for these kind of diagrams.
Which is mostly coloured boxes, and it's amazing how much you can show just using coloured boxes... but the trick of the trade is picking the *right* coloured boxes!
So some of the illustrations in the book are tried and tested ones that I've developed and refined over several years of training use, and have repurposed for the book – because there's no point reinventing the wheel.
(As an aside, I love that developers reinvented the 'reinventing the wheel' saying and called it 'not invented here' instead!)
Some of the illustrations are based off ones that already existed in our library, but where the existing illustrations didn;t quite work to describe the concept being discussed in the book.
Coming back to garbage collection, I have an existing template than I use for most of my parallel GC illustrations, but some of what we were showing in the book was new material, and so I needed to add to the existing representations. For example the attached illustration shows what happens when dealing with arrays in memory, which was something we'd not needed to explicitly show in the past, so I needed to find a way of showing contiguous blocks of memory.
And some of the illustrations are brand new and drawn specifically for Opimizing Java, but using the existing visual language (those coloured boxes again!)
In all cases, the original illustrations had been created in keynote, so I also redrew everything in illustrator which is a more appropriate for creating files for print. I did originally start to try to translate the illustrations into black/white/greyscale – which was tricky as the colour helps convey a lot of information in some illustrations – but luckily O'Reilly made the call to publish the book in full colour, which has made a big difference.
(Thank you O'Reilly!)