Scala入门一——单击版wordcount

单机版wordcount

/**
  * @author ${user}
  */
object WordCount {

  def main(args: Array[String]): Unit = {

    //定义集合
    val lines = List("hello tom hello jerry jerry","hello kitty jerry kitty hello hello")
    //println(lines.map(_.split(" ")))

    //获取到集合中的元素，并压平
    val flat = lines.map(_.split(" ")).flatten
    //println(flat)

    //flatMap 相当于先map再flatten
    val words = lines.flatMap(_.split(" "))//List(hello, tom, hello, jerry, hello, kitty, hello, hello)
    //println(flat1)
    //将集合输出到map
    val wordsAndOne = words.map((_,1))
    //println(wordsAndOne)//List((hello,1), (tom,1), (hello,1), (jerry,1), (hello,1), (kitty,1), (hello,1), (hello,1))

    //按照元组里面的第一个元素分组
    val group = wordsAndOne.groupBy(_._1)
    //group 结果为：Map(tom -> List((tom,1)), kitty -> List((kitty,1)), jerry -> List((jerry,1)), hello -> List((hello,1), (hello,1), (hello,1), (hello,1), (hello,1)))
    //println(group)

    val res = group.map(x => (x._1,x._2.size))
    println(res)//Map(tom -> 1, kitty -> 1, jerry -> 1, hello -> 5)

    //该代码和上一行代码等价
    val res1 = group.mapValues(_.size)
    println(res1)//Map(tom -> 1, kitty -> 2, jerry -> 3, hello -> 5)

    val res2 = group.mapValues(_.foldLeft(0)(_+_._2))
    println("res2结果为:"+res2)//res2:Map(tom -> 1, kitty -> 2, jerry -> 3, hello -> 5)
    //排序
    val finalRes = res.toList.sortBy(_._2).reverse
    println(finalRes)//List((hello,5), (jerry,1), (kitty,1), (tom,1))
  }

}