scala高阶函数--groupby/sortby/patition
作者:互联网
package day3 object demo_high_func { def main(args: Array[String]): Unit = { val list = Array(1,2,3,4,5,6,7,7,7,2,8) // 过滤数组中的元素, 将为true的元素组合成一个新的数组 val list2 = list.filter(e=>e%2==0) println(list2.mkString("[",",","]")) // map函数,对每个元素操作 println("-" * 40 + "map" + "-" * 40) val list3 = list.map(n=>n * 10) println(list3.mkString("[",",","]")) println("-" * 40 + "flatMap" + "-" * 40) val words = Array("hello you", "hello me", "hello other") val flist = words.flatMap(word=>word.split(" ")) println(flist.mkString("[",",","]")) println("-" * 40 + "reduce" + "-" * 40) //聚合函数, 啥意思看打印结果吧 val relist = list.reduce((a1,a2)=>{ println("v1= " + a1 + ",v2=" +a2) a1 + a2 }) // 普通写法 val res = list.reduce((v1,v2)=>v1+v2) //简单写法 val res1 = list.reduce(_ + _) println(res) println(res1) println("-" * 40 + "drowhile" + "-" * 40) val droplist = list.dropWhile(n=>n!=3) println(droplist.mkString("[",",","]")) println("-" * 40 + "sortwith" + "-" * 40) val newlist = Array(1,3,8,4,-1,7,6,10) val sortlist = newlist.sortWith((n1,n2)=>n1>n2) // 从大到小排序 val sortlist2 = newlist.sortWith(_ > _) // 简写 println(newlist.mkString("[",",","]")) println(sortlist.mkString("[",",","]")) println(sortlist2.mkString("[",",","]")) println("-" * 40 + "groupby" + "-" * 40) // 相当于sql中的group by , 返回值为不可变的map类型 val wordmap:Map[String,Array[String]] = flist.groupBy(word => word) // println(wordmap.mkString("[",",","]")) wordmap.foreach(kv=>println(kv._1,kv._2.mkString("[",",","]"))) println("-" * 40 + "partition" + "-" * 40) // 将一个集合分成两个, 能被2整除的放一个集合, 返回两个集合 val(left, right) = newlist.partition(n => n%2==0) println(left.mkString("[",",","]")) println(right.mkString("[",",","]")) } }
package day3 object demo_high_func { def main(args: Array[String]): Unit = { val list = Array(1,2,3,4,5,6,7,7,7,2,8) // 过滤数组中的元素, 将为true的元素组合成一个新的数组 val list2 = list.filter(e=>e%2==0) println(list2.mkString("[",",","]")) // map函数,对每个元素操作 println("-" * 40 + "map" + "-" * 40) val list3 = list.map(n=>n * 10) println(list3.mkString("[",",","]")) println("-" * 40 + "flatMap" + "-" * 40) val words = Array("hello you", "hello me", "hello other") val flist = words.flatMap(word=>word.split(" ")) println(flist.mkString("[",",","]")) println("-" * 40 + "reduce" + "-" * 40) //聚合函数, 啥意思看打印结果吧 val relist = list.reduce((a1,a2)=>{ println("v1= " + a1 + ",v2=" +a2) a1 + a2 }) // 普通写法 val res = list.reduce((v1,v2)=>v1+v2) //简单写法 val res1 = list.reduce(_ + _) println(res) println(res1) println("-" * 40 + "drowhile" + "-" * 40) val droplist = list.dropWhile(n=>n!=3) println(droplist.mkString("[",",","]")) println("-" * 40 + "sortwith" + "-" * 40) val newlist = Array(1,3,8,4,-1,7,6,10) val sortlist = newlist.sortWith((n1,n2)=>n1>n2) // 从大到小排序 val sortlist2 = newlist.sortWith(_ > _) // 简写 println(newlist.mkString("[",",","]")) println(sortlist.mkString("[",",","]")) println(sortlist2.mkString("[",",","]")) println("-" * 40 + "groupby" + "-" * 40) // 相当于sql中的group by , 返回值为不可变的map类型 val wordmap:Map[String,Array[String]] = flist.groupBy(word => word) // println(wordmap.mkString("[",",","]")) wordmap.foreach(kv=>println(kv._1,kv._2.mkString("[",",","]"))) println("-" * 40 + "partition" + "-" * 40) // 将一个集合分成两个, 能被2整除的放一个集合, 返回两个集合 val(left, right) = newlist.partition(n => n%2==0) println(left.mkString("[",",","]")) println(right.mkString("[",",","]")) } }
标签:val,scala,--,newlist,list,40,sortby,println,mkString 来源: https://www.cnblogs.com/kongzhagen/p/15159666.html