计算平均年龄

package scala

import scala.io.Source

object Demo23Student {
  def main(args: Array[String]): Unit = {
    /**
      * 统计班级的平均年龄
      *
      */
    //1、读取学生数据
    val students: List[String] = Source.fromFile("data/students.txt").getLines().toList

    //取出班级和年龄
    val clazzAndage: List[(String, Int)] =students.map((student: String ) => {
      val split: Array[String] = student.split(",")
      val clazz: String = split(4)
      val age: Int = split(2).toInt
      (clazz,age)
    })

    //3、将同一个班级分到同一个组内
    val group: Map[String, List[(String, Int)]] = clazzAndage.groupBy((kv:(String,Int )) => kv._1)

    //4、统计班级的平均年龄
    val clazzAvgAge: Map[String, Double] =group.map((kv:(String ,List[(String ,Int )])) => {
      val clazz: String = kv._1
      val clazzs: List[(String, Int)] = kv._2

      //取出年龄
      val ages: List[Int] = clazzs.map((i:(String ,Int )) => i._2)

      //计算平均年龄
      val avgAge :Double= ages.sum / ages.length.toDouble

      (clazz,avgAge)
    })

    clazzAvgAge.foreach(println)

  }
}