Re: [scala] Risks of using Scala in a large application?

Scala seems to me, from my quick introduction, what Java may be like  
in 5+ years.

I'd guess more like 10 years.  Java evolution has gotten very slow, compared to the level of gap between Java and Scala.

The low risk situation would be that Java and Scala are completely  
interchangeable, if I write something now in Scala it won't limit me  
and I could replace it with Java in the future if need be (e.g. if/
when Java catches up and/or Scala doesn't catch on) without any trouble.

From the point of view of technical risk, this low-risk situation is pretty close to the truth.  Moreover, the Scala team seems to have a high level of commitment to keeping it that way.


Of course there are other risk: finding developers that are competent  
enough in Scala, IDE tooling for Scala, longevity of Scala, and any  
discussion of these would also be appreciated.


While recruiting and tooling risks are certainly important, a larger issue is that the evolution of Scala is driven by a pretty small team, and their orientation is academic rather than commercial.  While this certainly has great benefits in terms of both language quality and rate of evolution, it does raise some risks with regard to the predictability of that evolution.  With a language like Java, you can make some pretty good guesses as to what it will look like 5 years from now.  With Scala, it's tough to guess what it will look like next Christmas (other than that it will be great).  This aggravates other risks, as developers become reluctant to train toward a moving target, and tool makers become skittish of the dev costs of supporting one.  This risk isn't a killer, but may explain some conservatism you may encounter about moving to Scala.