class Author(val company: String, val twitterHandle: String)

  def twitterHandles(authors: List[Author], company: String) = {

    authors.filter(_.company == company)
      .map(_.twitterHandle)
      .filter(_ != null)
  }

  def main(args: Array[String]) {

    val x = List(
                new Author("c1", "ct1"),
                new Author("c1", "ct2"),
                new Author("c2", "t3"),
                new Author("c1", null),
                new Author("c1", "ct5"),
                new Author("c5", "t6")
            )

    println(twitterHandles(x, "c1"))
    println(twitterHandles(x, "c2"))
    println(twitterHandles(x, "c00"))
  }