Origins of Scala, An Interview with Martin Odersky

http://www.artima.com/scalazine/articles/origins_of_scala.html

It is interesting that Odersky developed the GJ (Generic Java, which was Java with generics) compiler by 1998. That compiler was adopted by Sun for Java 1.3 (in 2000), because it was more maintainable than Sun's original 'javac'. Though, it's 'generic' features were not used, of course, until Java 5.

At the end of the article, Odersky touches on one good reason a new language was needed: the so-called covariant arrays problem.