Scala is short for Scalable Language. It smoothly integrates features of object-oriented and functional languages and its syntax is similar to Java. It has a very tight integration with Java and its byte code runs on the JVM.

Resources:

• Excellent introduction by Daniel Spiewak from a Java developer's perspective: Scala for Java refugees
• IBM developerWorks Scala series: The busy Java developer's guide to Scala
• Scala language features overview presentation by Jonas Bonér at Oredev, Nov 2009
• Dean Wampler's blog posts at Object Mentor about Scala
• http://debasishg.blogspot.com/2010/07/refactoring-into-scala-type-classes.html 

Observer pattern

trait Subject {
  private var observers : List[(Subject) => Any] = Nil
  def addObserver( cmd:(Subject) => Any ) = observers = cmd :: observers
  def notifyObservers() = observers.foreach( _(this) )
}