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“There are three kinds of variance: invariance, covariance, and contravariance…”
It looks pretty scary already, doesn’t it? If we search Wikipedia, we will find covariance and contravariance in category theory and linear algebra. Some of you who learned these subjects in university might be having dreadful flashbacks because it can be complex stuff.
When I started to prepare a course of lectures on the Java language for the Moscow Institute of Physics and Technology, I became to search for material that can be used as illustrations. ‘One picture is worth a thousand words’ as they say, and sometimes it’s worth even more because it seems impossible to explain e. g. how a hash table works without drawing something. My task was to explain to students many Java concepts, from string pool to advanced data structures. I was looking for a solution that is able to make the visualization of Java data structures in the easiest and precise way, ideally compatible with ‘presentation as code’ technology.
There exists Aleksey Shipilev’s JOL (Java Object Layout) tool known among Java performance engineers. JOL analyzes the memory layout for any given object, including all the auxiliary data and fields, and the graph of objects reachable from the given instance. This tool gives accurate estimations of the object size and also shows the addresses in memory where objects are located. However, it’s not yet able to visualize the object graph and gives too many low-level details that are irrelevant for the students who just started to learn Java.
I must have created dozens of presentations for colleagues, customers, and public appearances over the course of my IT career. PowerPoint has been my most natural and reliable slide-making choice for many years. But this year the situation has changed radically. Between February and May, I had the chance to speak at five conferences, and the slides for the reports had to be prepared very quickly and in high quality. Delegating the part of the work that entailed visual slide design to other people did cross my mind.
Once I tried to work with a designer by e-mailing .pptx files back and forth, but the work had turned into chaos: no one knew which version of the slides was the latest, and the layout was seriously off due to PowerPoint and the fonts' version discrepancies on our machines. That’s when I decided to try something new. I did try it, and I haven’t considered going back to PowerPoint since.
It may be argued that IntelliJ IDEA has the most advanced static Java code analyzer, whose capabilities leaves "veterans" like Checkstyle and Spotbugs far behind. Its many “inspections” check various aspects of the code, from coding style to certain kinds of bugs.
You may also enjoy: IntelliJ IDEA Essentials (RefCard)
However, as long as the results of the analysis are visible only to a sole developer in her IDE, they are of little use in the software delivery process. Static analysis should be performed as the first step of the delivery pipeline, and the build should fail if the results of this step don’t pass quality gates. JetBrains' TeamCity CI is known to be integrated with IDEA. Less known is the fact that even if you are not using TeamCity, you may run IDEA inspections on any other CI server. Let’s see how this may be done using the IDEA Community Edition, Jenkins, and the Warnings NG plugin.
This article is an authorized translation of my post in Russian. The translation was made with the kind help of the guys from PVS-Studio.
What encouraged me to write this article is a considerable quantity of materials on static analysis, which recently has been increasingly coming up. Firstly, this is a blog of PVS-Studio, which actively promotes itself posting reviews of errors found by their tool in open source projects. PVS-Studio has recently implemented Java support, and, of course, developers from IntelliJ IDEA, whose built-in analyzer is probably the most advanced for Java today, could not stay away.