10-1 集合之Map

mapValues，改造v

scala> val m = Map(2->"www",3->"ee",1->"rrrr")
m: scala.collection.Map[Int,String] = Map(2 -> www, 3 -> ee, 1 -> rrrr)

scala> m.mapValues(_.length)
res109: scala.collection.Map[Int,Int] = Map(2 -> 3, 3 -> 2, 1 -> 4)

map

scala> m.map(t => (t._1,t._2.length))
res112: scala.collection.Map[Int,Int] = Map(2 -> 3, 3 -> 2, 1 -> 4)

count

scala> m.count
   def count(p: ((Int, String)) => Boolean): Int

scala> m.count(t=>t._2.length>=3)
res114: Int = 2

渐变 --> 突变