Scala中算子练习、map()、filter()、sortBy()、reverse、grouped()、flatten()、flatMap()、reduceLeft() 23

左手的ㄟ右手 2022-01-27 05:45 175阅读 0赞

import scala.collection.parallel.immutable.ParSeq
    
    /** * */
    object ListTest { 
      def main(args: Array[String]): Unit = { 
        //创建一个List
        val list0=List(1,7,9,8,0,3,5,4,6,2)
    
        //1 将list0中的每一个元素乘以10后生成一个新的集合
        val list1=list0.map(_*10)
        println("list1==== "+list1)
    
        //2将list0中的偶数取出来生成一个新的集合
        val list2=list0.filter(_%2==0)
        println("list2==== "+list2)
    
        //3. 排序
        val list3: List[Int] = list0.sorted
        val list4: List[Int] = list0.sortBy(x => x)
        val sortWith: List[Int] = list0.sortWith(_>_)
        println(list3)
        println(list4)
        println("降序______________"+sortWith)
    
    
        //4. 反转
        val reverse: List[Int] = list3.reverse
        println("反转" + reverse)
    
        //5. 分组
        val list7: Iterator[List[Int]] = list0.grouped(4)
        println("list7==== "+list7)
    
        /*for (i <- list7){ println(i) }*/
    
        //将Iterator转换成List
        val list8=list7.toList
        println("list8==== "+list8)
    
        //9. 多个list压平, 也就是抽取出来
        val list9: List[Int] = list8.flatten
        println("list9---" + list9)
    
        val lines = List("hello tom hello jerry", "hello jerry", "hello kitty")
        //先按空格切分，在压平
    
        val result1: List[String] = lines.flatMap(_.split(" "))
        println(result1)
    
    
        //并行计算求和
        val sum: Int = list0.par.sum
        println(sum)
    
        //reduce 计算
        val sumReduce: Int = list0.reduce(_+_)
        println("sumReduce===="+sumReduce)
    
        //有特定顺序
        val left: Int = list0.reduceLeft(_+_)
        val right: Int = list0.reduceRight(_+_)
        println(left)
        println(right)
    
    
        //折叠
        val fold: Int = list0.fold(100)(_+_)
        println("fold=="+fold)
    
        //聚合
        val  list10= List(List(1, 2, 3), List(4, 5, 6), List(7,8), List(9,0))
        val par: ParSeq[List[Int]] = list10.par
        println("par--------------"+par)
        val aggregate: Int = par.aggregate(10)(_+_.sum,_+_)
        println(aggregate)
    
        //获取到参与并行计算的线程
        println(list10.par.collect{ 
          case _=>Thread.currentThread().getName
        }.distinct)
    
    
        val l1 = List(5,6,4,7)
        val l2 = List(1,2,3,4)
        //求并集
    
        val union: List[Int] = l1.union(l2)
        val intersect: List[Int] = l1.intersect(l2)
        println(union)
        println(intersect)
    
        //求差集
        val r3=l1.diff(l2)
        println("r3=== "+r3)
      }
    
    
    }