object LengthByFoldLeft { def length[T](as: List[T]): Int = FoldLeft.foldLeft(as, 0)((acc, _) => acc + 1) def main(args: Array[String]): Unit = { println(length(Nil)) println(length(List(1, 2, 3, 4))) println(length(List(1, 2, "a", 4))) println(length(List(1))) } }
0 4 4 1
原文：http://www.cnblogs.com/JonkeyGuan/p/5410483.html