[TOC]

# 定義

~~~

//初始化一個長度為8的定長數組,其所有元素均為0

val arr1 = new Array[Int](8)

//直接打印定長數組,內容為數組的hashcode值

println(arr1)

//將數組轉換為數組緩沖,就可以看到原數組的內容了

//toBuffer會將數組轉換為長數組緩沖

println(arr1.toBuffer)

//注意: 如果new,相當于調用了數組的apply方法,直接為數組賦值

//初始化一個長度為1的定長數組

val arr2 = Array[Int](10)

println(arr1.toBuffer)

//定義一個長度為3的定長數組

val arr3 = Array("hadoop", "storm", "spark")

//使用()來訪問元素

println(arr3(2))

~~~

# 賦值及取值

~~~

//等價于 arr2(1)=10

scala> arr2.update(1,10)

scala> arr2

res6: Array[Int] = Array(1, 10, 3)

~~~

也可以通過apply來取值

~~~

scala> arr2.apply(1)

res9: Int = 10

~~~

# 變長數組

需要打包

~~~

# _表示導入這個包下的所有

scala> import scala.collection.mutable._

import scala.collection.mutable._

scala> val ab = new ArrayBuffer[Int]()

ab: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> val arrBuffer1 = scala.collection.mutable.ArrayBuffer[Int](10,9,8)

arrBuffer1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(10, 9, 8)

~~~

## 追加元素

~~~

# 向尾部追加

scala> ab += 1

res0: ab.type = ArrayBuffer(1)

scala> ab += (3, 4, 5)

res1: ab.type = ArrayBuffer(1, 3, 4, 5)

# 追加一個數組緩沖

scala> ab ++= Array(6, 7)

res2: ab.type = ArrayBuffer(1, 3, 4, 5, 6, 7)

# 追加一個數組緩沖

scala> ab ++= ArrayBuffer(8, 9)

res3: ab.type = ArrayBuffer(1, 3, 4, 5, 6, 7, 8, 9)

# 向尾部追加

ab.append(123)

~~~

指定位置插入用insert

~~~

# 在0這個位置插入-1和0

ab.insert(0, -1, 0)

~~~

會生成一個新的數組

~~~

scala> ab :+ 99

res14: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(123, 3, 99)

scala> ab

res15: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(123, 3)

~~~

## 刪除

~~~

scala> ab

res5: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(-1, 0, 1, 3, 4, 5, 6, 7, 8, 9)

# 刪除數組某個位置的元素

# 在3這個位置移除2個

scala> ab.remove(3, 2)

scala> ab

res7: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(-1, 0, 1, 5, 6, 7, 8, 9)

~~~

## 定長數組和變長數組的轉換

~~~

scala> arr2.toBuffer

res7: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1, 10, 3)

scala> arr2.toArray

res8: Array[Int] = Array(1, 10, 3)

~~~

# 排序

~~~

scala> val arr = Array(1, 9, 5, 7, 3, 2)

arr: Array[Int] = Array(1, 9, 5, 7, 3, 2)

~~~

**升序**

~~~

scala>arr.sorted

res0: Array[Int] = Array(1, 2, 3, 5, 7, 9)

~~~

**降序**

~~~

scala> arr.sorted.reverse

res2: Array[Int] = Array(9, 7, 5, 3, 2, 1)

~~~

~~~

scala> arr.sortWith(_>_)

res1: Array[Int] = Array(9, 7, 5, 3, 2, 1)

~~~

也可以這樣寫

~~~

scala> arr.sortWith( (x, y) => x > y )

res3: Array[Int] = Array(9, 7, 5, 3, 2, 1)

~~~

**轉換后排序**

~~~

scala> val arr = Array(1,2,3,4,10,100)

arr: Array[Int] = Array(1, 2, 3, 4, 10, 100)

scala> arr.sortBy(x => x+"")

res0: Array[Int] = Array(1, 10, 100, 2, 3, 4)

~~~

# 數組轉換

yield關鍵字將原始的數組進行轉換會產生一個新的數組,原始的數組不變

~~~

scala> var arr = Array(1, 2, 3, 4, 5, 6, 7)

arr: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7)

scala> val res = for(e

res: Array[Int] = Array(2, 4, 6, 8, 10, 12, 14)

scala> arr.map(_ * 2)

res0: Array[Int] = Array(2, 4, 6, 8, 10, 12, 14)

scala> arr

res1: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7)

~~~

# 過濾

偶數乘以10

~~~

scala> arr.filter(_ % 2 == 0).map(_ * 10)

res2: Array[Int] = Array(20, 40, 60)

~~~

# 常用方法

**求和**

~~~

scala> arr

res3: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7)

scala> arr.sum

res4: Int = 28

//reduce匯總

scala> arr.reduce(_+_)

res5: Int = 28

~~~

**給初始值求和**

~~~

scala> arr.fold(10)(_+_)

res1: Int = 38

~~~

**求最大值**

~~~

arr.max

~~~

**切分和壓平**

flatten和map()

~~~

scala> val a = Array("a b c", "d e f", "h i j")

a: Array[String] = Array(a b c, d e f, h i j)

scala> a.map(_.split(" "))

res1: Array[Array[String]] = Array(Array(a, b, c), Array(d, e, f), Array(h, i, j))

scala> a.flatMap(_.split(" "))

res4: Array[String] = Array(a, b, c, d, e, f, h, i, j)

~~~

# 轉換為String

~~~

scala> val arr2 = Array(1,2,3)

arr2: Array[Int] = Array(1, 2, 3)

scala> arr2.mkString(",")

res4: String = 1,2,3

~~~

# 多維數組

## 定義

~~~

scala> val arr4 = Array.ofDim[Int](3, 4)

arr4: Array[Array[Int]] = Array(Array(0, 0, 0, 0), Array(0, 0, 0, 0), Array(0, 0, 0, 0))

scala> arr4.mkString(" ")

res16: String = [I@22b8eaf0 [I@50dfceff [I@26a5007

scala> for(x

0,0,0,0

0,0,0,0

0,0,0,0

~~~

賦值

~~~

scala> arr4(1)(2) = 1

~~~

# 與java數組互相轉換

scala數組轉java數組

~~~

import scala.collection.mutable.ArrayBuffer

val arr4 = ArrayBuffer("1", "2", "3")

// scala to java

import scala.collection.JavaConversions.bufferAsJavaList

val javaArr = new ProcessBuilder(arr4)

println(javaArr.command())

~~~

java數組轉scala數組

~~~

import scala.collection.mutable.ArrayBuffer

val arr4 = ArrayBuffer("1", "2", "3")

//_表示導入這個包下的所有

import scala.collection.JavaConversions._

import scala.collection.mutable.Buffer

// scala to java

val javaArr = new ProcessBuilder(arr4)

//java to scala

val scalaArr: Buffer[String] = javaArr.command()

println(scalaArr)

~~~

總結

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