Tip of the Iceberg

Category xpages java
If you're a Domino developer, you're likely already developing XPage applications or headed in that direction. And if you're already developing with XPages, you're likely at least curious about Java, if not already familiar with at least a few concepts of the language.

I'm asked with increasing frequency, "how should I start learning Java?" That's not a surprising question, given both the complexity of the language and the sheer amount of information available; it's comparatively easy to learn LotusScript, because it's a comparatively finite language and there is a single authoritative source: Domino Designer Help. And, let's face it, there are simply less people using LotusScript than Java. While a community of literally millions of developers can be an advantageous resource once you're comfortable with the language, if you're wondering how to even begin, that's a lot of hay to discard just to find your first needle.

One approach, of course, is to find a good book. I've consistently heard great things about Head First Java (though I've never read it myself). Of late, however, I find I'm recommending to developers new to the language, and to those with some familiarity who want to apply that familiarity specifically to XPage development, this tutorial on the Java Collections Framework.

Every Notes / Domino developer is already familiar with the philosophy of a collection: it's just a way to refer to multiple things by a single name. In LotusScript, we have arrays and Lists. But even Notes Formula has lists. So we already get the concept, now we just need to update our terminology.

For example, a list in Formula is not the same as a List in LotusScript; a Formula list is really more akin to a LotusScript array. A LotusScript List, on the other hand, is a construct used to map keys to values: for instance, names to phone numbers.

Similarly, a List in Java is like a LotusScript array or a Formula List; a Java Map is like a LotusScript List.

If you haven't already finished the above tutorial, sorry to spoil the suprise, but the previous sentence already tells you most of what you need to know. Reading the full tutorial is a great way to quickly come up to speed on all the interfaces that comprise the Collections Framework - particularly the methods each supports - but if you only understand List and Map, you're already well on your way to writing better XPages... even if you never write a single line of Java. The true "nuts and bolts" of XPages are Lists and Maps, so even if your own code is strictly SSJS, that code is still interacting with Lists and Maps, and understanding what those are and how they work will make your results far more predictable.