rdd转换为Set或者Map

rdd转Set

val toSet: Set[String] = file.map(u => {  strings ++= Set(u)   strings}).collect().flatten.toSet

rdd转Map

val appdict = sc.textFile(appfilePath).map {  line => {    val fields = line.split("\t", line.length)    var map = Map[String, String]()    if (fields.length > 4) {      map += (fields(4) -> fields(1))    }    map  }}.collect().flatten.toMap