"Each time I pick one I end up giving up after 2 weeks as I always go back to Java": you don't want to leave your comfort zone, I guest. I suggest Scala. Start

"Each time I pick one I end up giving up after 2 weeks as I always go back to Java": you don't want to leave your comfort zone, I guest. I suggest Scala. Start with Scala for the Impatient a little bit and then Functional Programming in Scala.