"Guardian.co.uk Switching from Java to Scala"

http://www.infoq.com/articles/guardian_scala
(interview with Graham Tackley)

"After about four weeks of writing just the tests in Scala, we got fed
up of having to write the main code in Java, and decided to convert the
whole lot to Scala." [not the whole website yet]

"[Our build setup] allows Java and Scala code to co-exist in the same
project, and bi-directionally depend on each other. So we could convert
on a class-by-class basis from Java to Scala, which worked far better
than we ever imagined: it really did just work."

"It's true that due to the rigidity of Java individual lines of code are
always easily understood. But that's rarely the problem in understanding
any non-trivial codebase: I don't want to understand the detail, I want
to understand the intent. Good class design and OO techniques help
address this in Java, but I still often find when reading Java code that
I cannot see the wood for the trees... I tend to find that when reading
an individual line of code in Scala it sometimes takes a little longer
to understand how it's working, but this is more than made up for by the
drastic reduction in the number of lines of code."

"In the last six months, all of the new JVM-based projects have used
Scala and none have selected Java. I can't see us starting any new
project in Java now..."