Scala数组的定义

最新推荐文章于 2024-11-22 17:22:17 发布

lucasmaluping

最新推荐文章于 2024-11-22 17:22:17 发布

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本文链接：https://blog.youkuaiyun.com/lucasmaluping/article/details/99287522

本文深入探讨Scala中的数组定义与操作，包括使用Array类创建数组、元素的读写、数组的映射(map)与扁平化(flatten)操作，以及如何进行WordCount统计。通过实例演示了Scala数组的灵活性和强大功能。

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定义方式，可以new

scala> val arr = new Array[Int](3)
arr: Array[Int] = Array(0, 0, 0)

scala> arr[0] = 100
<console>:1: error: identifier expected but integer literal found.
arr[0] = 100
^

在scala中用（）

scala> arr(0) = 100

scala> arr(0)
res5: Int = 100

定义方式2：

scala> val arr = Array[Int](1,2,3,4,5)
arr: Array[Int] = Array(1, 2, 3, 4, 5)

scala> arr(1) = 100;

内容可变，长度不可变

scala> arr += 8
<console>:13: error: value += is not a member of Array[Int]
arr += 8
^

scala> fx = (x: Int) => x * 10
<console>:13: error: not found: value fx
val $ires0 = fx
^
<console>:11: error: not found: value fx
fx = (x: Int) => x * 10
^

//arr经过map映射操作之后，会返回一个新的数组

scala> val fx = (x: Int) => x * 10
fx: Int => Int = <function1>

scala> arr.map(fx)
res8: Array[Int] = Array(10, 1000, 30, 40, 50)

scala> arr
res9: Array[Int] = Array(1, 100, 3, 4, 5)

//arr经过map映射操作之后，会返回一个新的数组

scala> val fx = (x: Int) => x * 10
fx: Int => Int = <function1>

scala> arr.map(fx)
res8: Array[Int] = Array(10, 1000, 30, 40, 50)

scala> arr
res9: Array[Int] = Array(1, 100, 3, 4, 5)

flatten:扁平化

scala> val arr = Array("hello you hello me","hello nimoo hello jim")
arr: Array[String] = Array(hello you hello me, hello nimoo hello jim)

scala> arr.map(_.split(" "))
res10: Array[Array[String]] = Array(Array(hello, you, hello, me), Array(hello, nimoo, hello, jim))

scala> arr.map(_.split(" ")).faltten
<console>:13: error: value faltten is not a member of Array[Array[String]]
arr.map(_.split(" ")).faltten
^

scala> arr.map(_.split(" ")).flatten
res12: Array[String] = Array(hello, you, hello, me, hello, nimoo, hello, jim)

map+ flatten

scala> arr.flatMap(_.split(" "))
res13: Array[String] = Array(hello, you, hello, me, hello, nimoo, hello, jim)

求WordCount

scala> arr
res16: Array[String] = Array(hello you hello me, hello nimoo hello jim)

scala> arr.flatMap(_.split(" ")).groupBy(x => x)
res17: scala.collection.immutable.Map[String,Array[String]] = Map(nimoo -> Array(nimoo), you -> Array(you), jim -> Array(jim), me -> Array(me), hello -> Array(hello, hello, hello, hello))

scala> arr.flatMap(_.split(" ")).groupBy(x => x).mapValues(_.length)
res18: scala.collection.immutable.Map[String,Int] = Map(nimoo -> 1, you -> 1, jim -> 1, me -> 1, hello -> 4)

scala> arr.flatMap(_.split(" ")).groupBy(x => x).mapValues(_.length).toList
res19: List[(String, Int)] = List((nimoo,1), (you,1), (jim,1), (me,1), (hello,4))

scala> arr.flatMap(_.split(" ")).groupBy(x => x).mapValues(_.length).toList.sortBy(x => x._2)
res20: List[(String, Int)] = List((nimoo,1), (you,1), (jim,1), (me,1), (hello,4))

scala> arr.flatMap(_.split(" ")).groupBy(x => x).mapValues(_.length).toList.sortBy(x => - x._2)
res21: List[(String, Int)] = List((hello,4), (nimoo,1), (you,1), (jim,1), (me,1))