Pardon me for playing with the title of Edsger Dijkstra's famous paper, but as a Java developer I am starting to believe that arrays should be seldom used, given Java generics and the revised collection classes. I started thinking about this while reading someone else's code and noticing some artificial looking conversions between arrays and collections. Then for fun, I did some measurement and noticed over 15% of processing time was spent in toArray() methods.
The big cost in IT is usually in development and maintenance, not in deployment costs. Most projects are small, not Amazon size deployments so I believe that unless you are sure that you are building a very large scale system, it is best to optimize development to reduce costs for small and medium size systems. Smaller code size means smaller costs. Java programs should be as short and concise as possible and generics and use of collections helps a lot. Sometimes when I read the source for Java programs it looks like the authors were paid by line of code :-)