大数据学习——scala集合练习

╰半夏微凉° 2021-12-12 13:17 324阅读 0赞

package com
    
    /**
      * Created by ZX on 2016/4/5.
      */
    object ListTest {
      def main(args: Array[String]) {
        //创建一个List
        val lst0 = List(1,7,9,8,0,3,5,4,6,2)
        //将lst0中每个元素乘以10后生成一个新的集合
        val lst01=lst0.map(_ * 10)
        println("lst01"+lst01)
    
        val lst1 = lst0.map(x => x * 2)
        //将lst0中的偶数取出来生成一个新的集合
        val lst02=lst0.filter(_ % 2==0)
        println("lst02"+lst02)
    
        val lst2 = lst0.filter(x => x % 2 == 0)
        //将lst0排序后生成一个新的集合
        //正序
        val lst03=lst0.sorted
        println("lst03"+lst03)
        //倒序
        val lst04=lst0.sorted.reverse
        println("lst04"+lst04)
    
    
        val lst3 = lst0.sorted
        val lst4 = lst0.sortBy(x => x)
        val lst5 = lst0.sortWith((x, y) => x < y)
        //反转顺序
        val lst6 = lst3.reverse
        //将lst0中的元素4个一组,类型为Iterator[List[Int]]
    
        val lst05=lst0.grouped(4)
    //    println("lst05"+lst05.toList)
    
        val it = lst0.grouped(4)
        //将Iterator转换成List
        val lst7 = it.toList
        //将多个list压扁成一个List
        val lst8 = lst7.flatten
    
        val lst06=lst05.toList.flatten
        println("lst06"+lst06)
    
        //先按空格切分，在压平
        val a = Array("a b c", "d e f", "h i j")
        val lst07=a.flatMap(_.split(" "))
        println("lst07"+lst07.toList.flatten)
    
        a.flatMap(_.split(" "))
    
        lst0.reduce(_+_)
        lst0.fold(10)(_+_)
    
        //并行计算求和
        lst0.par.sum
        lst0.par.map(_ % 2 == 0)
        lst0.par.reduce((x, y) => x + y)
        //化简：reduce
        //将非特定顺序的二元操作应用到所有元素
        val lst9 = lst0.par.reduce((x, y) => x + y)
        //按照特定的顺序
        val lst10 = lst0.reduceLeft(_+_)
    
        //折叠：有初始值（无特定顺序）
        val lst11 = lst0.par.fold(100)((x, y) => x + y)
        //折叠：有初始值（有特定顺序）
        val lst12 = lst0.foldLeft(100)((x, y) => x + y)
    
    
        //聚合
        val arr = List(List(1, 2, 3), List(3, 4, 5), List(2), List(0))
        val result = arr.aggregate(0)(_+_.sum, _+_)
    
        val l1 = List(5,6,4,7)
        val l2 = List(1,2,3,4)
        //求并集
        val r1 = l1.union(l2)
        //求交集
        val r2 = l1.intersect(l2)
        //求差集
        val r3 = l1.diff(l2)
        val r4 = l2.diff(l1)
        println(r1)
        println(r2)
        println(r3)
        println(r4)
    
        val m = Map(("a", 1))
    
      }
    }

val array = Array(1, 2, 3, 4, 5)
        println(array.fold(0)(_ + _))
    //结果15  0+1+2+3+4+5

//并行集合
        println(array.par.sum)
        println(array.par.reduce(_+_))
        println(array.reduceLeft(_+_))
        println(array.foldLeft(10)(_+_))

//聚合
        val arrList=List(List(100,2,3),List(3,4,5),List(4,5))
        val res=arrList.aggregate(10)(_+_.sum,_+_)
        println(res)

转载于:https://www.cnblogs.com/feifeicui/p/10967085.html