scala02课件
函数得定义
val funtionName=(param:ParamType...)=>{}
这种定义方式没有返回值类型，会自己进行适配
函数在scala中可以任务是一个可以使用得值
函数在放置得时候会显示签名信息，描述当前函数得一个描述信息文件
eg:在scala中存在三种类型 class类 object对象 trait特质（接口）
定义得函数其实在scala内部已经存在模板，function0-function22我们根据参数得数量不一致可以得出23中函数
函数定义得复杂形式
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scala> val add:(Int,Int)=>Int=(x,y)=>{x+y} add: (Int, Int) => Int = <function2> |
val func:(paramType...)=>returnType=(param...)=>{content}
如果直接放置函数则显示得是签名信息 function()调用
高级函数得使用
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scala> val a:(Int,Int)=>Int = add a: (Int, Int) => Int = <function2> scala> val b:(Int,Int)=>Int=add b: (Int, Int) => Int = <function2> |
函数得放置类型，函数可以作为返回值
函数作为参数传递
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scala> calculate(1,2,add) res10: Int = 3 scala> val cj=(x:Int,y:Int)=>x*y cj: (Int, Int) => Int = <function2> scala> calculate(2,3,cj) res11: Int = 6 scala> calculate(3,4,(x:Int,y:Int)=>x%y) res12: Int = 3 |
注意函数得泛型
函数和方法几乎是一个东西？
函数和方法得相互转换？
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scala> val sum=(x:Int,y:Int)=>x+y sum: (Int, Int) => Int = <function2> scala> sum res14: (Int, Int) => Int = <function2> scala> add _ res15: (Int, Int) => Int = <function2> scala> res15(1,2) res16: Int = 3 scala> add _(2,3) <console>:1: error: ';' expected but '(' found. add _(2,3) ^ scala> (add _)(3,4) res17: Int = 7 |
函数能够作为方法得参数，如果将方法也放入到方法得参数中
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scala> (add _)(3,4) res17: Int = 7 scala> calculate(2,3,add _) res18: Int = 5 scala> calculate(2,3,add) res19: Int = 5 |
在默认情况下，方法如果作为参数了，那么可以自动转换为函数
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scala> println _ res21: () => Unit = <function0> scala> println(1,2,3,4,5) (1,2,3,4,5) scala> var arr = Array(1,2,3,4,5,6,76) arr: Array[Int] = Array(1, 2, 3, 4, 5, 6, 76) scala> arr.foreach(println) 1 2 3 4 5 6 76 scala> arr.foreach(println _) |
经常使用得打印方法
总结：
- 函数和方法得定义方式不一样 def={} val=>
- 函数可以作为表达式单独存在，能够显示签名信息，但是方法只能被调用
- 函数是将scala中内置得function0-22得trait进行了实现
- 函数是scala中得头等公民
- 函数和方法得本质区别不大，默认情况下可以相互转换
- 方法转换为函数得时候 method _
- 其实还是方法使用得多
scala中得集合框架
在scala中集合框架分为两种immutable mutable
常用得五种框架
tuple元组类型 Array数组类型 list map set
元组tuple
一些列得数据得集合，不可变的
相当于对象，可以将一些完全不相关的数据放置在一起
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scala> var tp = ("zhangsan",3500) tp: (String, Int) = (zhangsan,3500) scala> var tp = ("zhangsan",35000,40,"fs") tp: (String, Int, Int, String) = (zhangsan,35000,40,fs) scala> val tp:(String,String,String)=("","","") tp: (String, String, String) = ("","","") scala> val tp = new Tuple[String,Int]("zhangsan",20000) <console>:11: error: not found: type Tuple val tp = new Tuple[String,Int]("zhangsan",20000) ^ scala> val tp = new Tuple2[String,Int]("zhangsan",20000) tp: (String, Int) = (zhangsan,20000) scala> val tp:Tuple2[String,Int]=("zhangsan",23000) tp: (String, Int) = (zhangsan,23000) scala> val tp:(String,Int) = new Tuple2[String,Int]("zhangsan",20000) tp: (String, Int) = (zhangsan,20000) |
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scala> tp._1 res25: String = zhangsan scala> tp._2 res26: Int = 20000 scala> tp res27: (String, Int) = (zhangsan,20000) scala> (1,tp) res28: (Int, (String, Int)) = (1,(zhangsan,20000)) scala> res28._2._1 res29: String = zhangsan |
元组是Tuple类的实例，总共存在Tuple1-22
取值的时候按照元素的名称取值_1到_N
一个特殊的元组对偶元组
两个元素的元组就是对偶元组
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scala> val tp:Tuple2[String,Int] = ("zhangsan",20000) tp: (String, Int) = (zhangsan,20000) scala> tp.swap res30: (Int, String) = (20000,zhangsan) |
对偶元组中存在一个swap方法进行元素的互换
对偶元组是map集合中的一个元素
zip拉链操作
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scala> var arr = Array("hello","world","tom","jack") arr: Array[String] = Array(hello, world, tom, jack) scala> var arr1 = Array(1,2,3) arr1: Array[Int] = Array(1, 2, 3) scala> arr zip arr1 res31: Array[(String, Int)] = Array((hello,1), (world,2), (tom,3)) scala> arr.zip(arr1) res32: Array[(String, Int)] = Array((hello,1), (world,2), (tom,3)) |
zip拉链操作完毕的数据是一个元组的array集合，按照木桶原理
zipWithIndex与下标进行拉链
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scala> arr res33: Array[String] = Array(hello, world, tom, jack) scala> arr.zipWithIndex res34: Array[(String, Int)] = Array((hello,0), (world,1), (tom,2), (jack,3)) |
与下标进行拉链操作，下标从0开始
数组Array
array存在两种 immutable mutable
scala.Array直接使用就是这个默认的，不可变的数组
scala.collection.mutable.ArrayBuffer可变数组
Array是长度不可变，但是元素可变
ArrayBuffer长度和元素都可以变化
数组的声明
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scala> var arr = Array(1,2,3,4,5,6) arr: Array[Int] = Array(1, 2, 3, 4, 5, 6) scala> var arr = new Array(3) arr: Array[Nothing] = Array(null, null, null) scala> arr(1)=3 <console>:13: error: type mismatch; found : Int(3) required: Nothing arr(1)=3 ^ scala> arr(0) java.lang.NullPointerException scala> var arr = new Array[Int](4) arr: Array[Int] = Array(0, 0, 0, 0) scala> var arr = new Array[Boolean](4) arr: Array[Boolean] = Array(false, false, false, false) |
取值方式 arr(index) 赋值arr(index)=N
声明的时候如果是new的数组，那么一定要指定泛型，不然泛型就是Nothing，不可以使用
Array的操作方法
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scala> arr:+1 res38: Array[AnyVal] = Array(false, false, false, false, 1) scala> arr:+23 res39: Array[AnyVal] = Array(false, false, false, false, 23) scala> arr res40: Array[Boolean] = Array(false, false, false, false) scala> arr ++ arr res41: Array[Boolean] = Array(false, false, false, false, false, false, false, false) scala> arr res42: Array[Boolean] = Array(false, false, false, false) scala> arr.isEmpty res43: Boolean = false scala> arr.max res44: Boolean = false scala> arr.min res45: Boolean = false scala> arr.sum <console>:13: error: could not find implicit value for parameter num: Numeric[Boolean] arr.sum ^ scala> var arr = Array(1,2,3,4,5,6) arr: Array[Int] = Array(1, 2, 3, 4, 5, 6) scala> arr.sum res47: Int = 21 scala> arr.length res48: Int = 6 scala> arr.size res49: Int = 6 |
sorted sortWith sortBy
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scala> var arr = Array(4,2,1,6,12,23) arr: Array[Int] = Array(4, 2, 1, 6, 12, 23) scala> arr.sorted res51: Array[Int] = Array(1, 2, 4, 6, 12, 23) scala> arr res55: Array[(String, Int)] = Array((zhangsan,56), (lisi,21), (wangwu,67)) scala> arr.sortBy def sortBy[B](f: ((String, Int)) => B)(implicit ord: scala.math.Ordering[B]): Array[(String, Int)] scala> arr.sortBy def sortBy[B](f: ((String, Int)) => B)(implicit ord: scala.math.Ordering[B]): Array[(String, Int)] scala> arr.sortBy((t:(String,Int))=>t._2) res56: Array[(String, Int)] = Array((lisi,21), (zhangsan,56), (wangwu,67)) scala> arr.sortBy((t:(String,Int))=> -t._2) res57: Array[(String, Int)] = Array((wangwu,67), (zhangsan,56), (lisi,21)) scala> arr.sortBy(t=>t._2) res58: Array[(String, Int)] = Array((lisi,21), (zhangsan,56), (wangwu,67)) scala> val func=(x:(String,Int))=>x._2 func: ((String, Int)) => Int = <function1> scala> arr.sortBy(func) res61: Array[(String, Int)] = Array((lisi,21), (zhangsan,56), (wangwu,67)) scala> arr.sortBy(t=>t._2) res62: Array[(String, Int)] = Array((lisi,21), (zhangsan,56), (wangwu,67)) scala> arr.sortBy(_._2) res63: Array[(String, Int)] = Array((lisi,21), (zhangsan,56), (wangwu,67)) |
sortWith与谁一起排序
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scala> arr.sortWith(func) res64: Array[(String, Int)] = Array((wangwu,67), (zhangsan,56), (lisi,21)) scala> val func=(x:(String,Int),y:(String,Int))=>x._2<y._2 func: ((String, Int), (String, Int)) => Boolean = <function2> scala> arr.sortWith(func) res65: Array[(String, Int)] = Array((lisi,21), (zhangsan,56), (wangwu,67)) scala> arr.sortWith((x:(String,Int),y:(String,Int))=>x._2>y._2) res66: Array[(String, Int)] = Array((wangwu,67), (zhangsan,56), (lisi,21)) scala> arr.sortWith((x,y)=>x._2>y._2) res67: Array[(String, Int)] = Array((wangwu,67), (zhangsan,56), (lisi,21)) scala> arr.sortWith(_._2>_._2) res68: Array[(String, Int)] = Array((wangwu,67), (zhangsan,56), (lisi,21)) |
记住下划线的使用方式，统配每一个元素
匿名函数的使用规则
sortWith是按照相邻的两个元素进行比较
以上三种排序方式适用所有的集合
ArrayBuffer可变数组
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scala> import scala.collection.mutable.ArrayBuffer import scala.collection.mutable.ArrayBuffer scala> var buff = ArrayBuffer(1,2,3,4,5,6) buff: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6) scala> var buff:ArrayBuffer[Int] = ArrayBuffer[Int](1,2,3,4,5,6) buff: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6) scala> var buff = new ArrayBuffer[Int](4) buff: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer() scala> var buff = new ArrayBuffer[Int]() buff: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer() |
在声明arrayBuffer的时候不能加上长度，因为arrayBuffer是长度可变的
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scala> buff res70: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer() scala> buff+=1 res71: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1) scala> buff res72: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1) scala> buff++=Array(1,2,3,4,5) res73: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 1, 2, 3, 4, 5) scala> buff res74: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 1, 2, 3, 4, 5) scala> buff-=(1) res75: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5) scala> buff--=Array(1,1,1,11,2,3,4) res76: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5) scala> buff.insert insert insertAll scala> buff.insert def insert(n: Int,elems: Int*): Unit scala> buff.insert(0,1,2,3,4,5,6,7,8) scala> buff res78: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6, 7, 8, 5) scala> buff.remove def remove(n: Int): Int override def remove(n: Int,count: Int): Unit scala> buff.remove(0) res79: Int = 1 scala> buff res80: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 3, 4, 5, 6, 7, 8, 5) scala> buff.remove(0,3) scala> buffer <console>:13: error: not found: value buffer buffer ^ scala> buff res83: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5, 6, 7, 8, 5) scala> buff.clear scala> buff res85: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer() scala> buff.isEmpty res86: Boolean = true |
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scala> arr.toBuffer res88: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1) scala> res88.toArray res89: Array[Int] = Array(1) |
数组练习题：
- 创建一个方法，方法中的参数是一个Array[Int]集合，求出这个数组的最大值，最小值，平均值，一次性返回
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scala> def getMMA(x:Array[Int]):(Int,Int,Double)={ | (x.max,x.min,x.sum*1.0/x.size) | } getMMA: (x: Array[Int])(Int, Int, Double) scala> getMMA(Array(1,2,3,4,5,6)) res94: (Int, Int, Double) = (6,1,3.5) |
List集合
scala.list不可变的，元素和长度都不可变
scala.collection.mutable.ListBuffer 长度和内容都可变
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scala> var list:List[Int]=List(1,2,3,4,54) list: List[Int] = List(1, 2, 3, 4, 54) scala> var list:List[Int]=List[Int](1,2,3,4,54) list: List[Int] = List(1, 2, 3, 4, 54) scala> var list = new List[Int](4) <console>:12: error: class List is abstract; cannot be instantiated var list = new List[Int](4) ^ scala> var list = 1::2::3::4::Nil list: List[Int] = List(1, 2, 3, 4) |
：：拼接，将元素和list集合进行拼接
Nil他是list的特殊形式，代表一个空的列表
var list = （1::（2::（3::（4::Nil））））拼接的时候从最右侧进行拼接
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scala> Nil res95: scala.collection.immutable.Nil.type = List() scala> 1::Nil res96: List[Int] = List(1) |
list中的元素和长度都不可以发生改变
取值的时候list(N)取第N个位置的元素
ListBuffer可变的集合
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scala> val buff = ListBuffer(1,2,3,4,5,6) <console>:12: error: not found: value ListBuffer val buff = ListBuffer(1,2,3,4,5,6) ^ scala> val buff = scala.collection.mutable.ListBuffer(1,2,3,4,5,6) buff: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 4, 5, 6) scala> import scala.collection.mutable.ListBuffer import scala.collection.mutable.ListBuffer scala> val buff = new ListBuffer[Int](3) <console>:13: error: too many arguments for constructor ListBuffer: ()scala.collection.mutable.ListBuffer[Int] val buff = new ListBuffer[Int](3) ^ scala> val buff = new ListBuffer[Int]() buff: scala.collection.mutable.ListBuffer[Int] = ListBuffer() |
-= --= += ++= insert remove clear isEmpty max min sum reverse....同ArrayBuffer
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scala> buff res106: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 1, 2, 3, 4, 5) scala> buff.toArray res107: Array[Int] = Array(1, 1, 2, 3, 4, 5) scala> buff.toBuffer res108: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1, 1, 2, 3, 4, 5) scala> Array().toBuffer res109: scala.collection.mutable.Buffer[Nothing] = ArrayBuffer() scala> var arr = Array(1,2,3,4,5) arr: Array[Int] = Array(1, 2, 3, 4, 5) scala> arr.toList res110: List[Int] = List(1, 2, 3, 4, 5) |
toBuffer转换的是ArrayBuffer toList转换为List toArray转换为array
Map也是两种，一种是可变的，一种不可变的
但是两种map都叫一个名字 Map
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scala> var map:Map[String,Int]=Map("zhangsan"->2000) map: Map[String,Int] = Map(zhangsan -> 2000) scala> var map = Map("zhangsan"->3500) map: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 3500) scala> var map = Map(("zhangsan",5000)) map: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 5000) |
元素和长度都不可以发生改变，创建的时候可以放入对偶元组
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scala> map+("lisi"->5000) res111: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 5000, lisi -> 5000) scala> map res112: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 5000) scala> map("zhangsan")=3400 <console>:15: error: value update is not a member of scala.collection.immutable.Map[String,Int] map("zhangsan")=3400 scala> val map = new scala.collection.immutable.HashMap[String,Int]() map: scala.collection.immutable.HashMap[String,Int] = Map() scala> map+("zhangsan"->2000) res114: scala.collection.immutable.HashMap[String,Int] = Map(zhangsan -> 2000) scala> map res115: scala.collection.immutable.HashMap[String,Int] = Map() scala> map ++ Map("zhangsan"->23111) res117: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 23111) scala> map res118: scala.collection.immutable.HashMap[String,Int] = Map() |
eg: ->是一个方法，指向k-v键值对的方法
不可变的map只能生成新的map集合 + ++
map的取值方式
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scala> map("zhangsan") res120: Int = 2000 scala> map("zhangsan1") java.util.NoSuchElementException: key not found: zhangsan1 at scala.collection.MapLike$class.default(MapLike.scala:228) at scala.collection.AbstractMap.default(Map.scala:59) at scala.collection.MapLike$class.apply(MapLike.scala:141) at scala.collection.AbstractMap.apply(Map.scala:59) ... 32 elided scala> map.get("zhangsan") res122: Option[Int] = Some(2000) scala> map.get("zhangsan1") res123: Option[Int] = None |
map(key)可以取值value
map.get(key)==>Option==>Some/None
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scala> map res126: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 2000) scala> map.get("zhangsan") res127: Option[Int] = Some(2000) scala> res127.get res128: Int = 2000 scala> map.get("zhangsan1") res129: Option[Int] = None scala> res129.get java.util.NoSuchElementException: None.get at scala.None$.get(Option.scala:347) at scala.None$.get(Option.scala:345) ... 32 elided scala> map.getOrElse("zhangsan1",3000) res131: Int = 3000 scala> map.getOrElse("zhangsan",3000) res132: Int = 2000 |
getOrElse可以取值，如果没有这个key，那么可以给一个默认值
可变map
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scala> map+=("lisi"->23456) res134: scala.collection.mutable.Map[String,Int] = Map(lisi -> 23456, zhangsan -> 20) scala> map res135: scala.collection.mutable.Map[String,Int] = Map(lisi -> 23456, zhangsan -> 20) scala> map++=Map("wangwu"->32000) res136: scala.collection.mutable.Map[String,Int] = Map(lisi -> 23456, zhangsan -> 20, wangwu -> 32000) scala> map res137: scala.collection.mutable.Map[String,Int] = Map(lisi -> 23456, zhangsan -> 20, wangwu -> 32000) scala> map-=("zhangsan") res138: scala.collection.mutable.Map[String,Int] = Map(lisi -> 23456, wangwu -> 32000) scala> map-=("zhangsan","lisi","zhaoliu") res139: scala.collection.mutable.Map[String,Int] = Map(wangwu -> 32000) scala> map--=Array("zhangsan","lisi") res140: scala.collection.mutable.Map[String,Int] = Map(wangwu -> 32000) scala> map.remove("zhaoliu") res141: Option[Int] = None scala> map.remove("wangwu") res142: Option[Int] = Some(32000) scala> map.put("zhangsan",2000) res143: Option[Int] = None scala> map res144: scala.collection.mutable.Map[String,Int] = Map(zhangsan -> 2000) |
keySet keys keysIterator values valuesIterator
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scala> var map = Map("zhangsan"->20000,"lisi"->30000,"wangwu"->49999) map: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 20000, lisi -> 30000, wangwu -> 49999) scala> map.keys res145: Iterable[String] = Set(zhangsan, lisi, wangwu) scala> map.keySet res146: scala.collection.immutable.Set[String] = Set(zhangsan, lisi, wangwu) scala> map.keysIterator res147: Iterator[String] = non-empty iterator scala> for(e<-map.keys){ | println(map(e)) | } 20000 30000 49999 scala> map.keysIterator res149: Iterator[String] = non-empty iterator scala> while(res149.hasNext){ | println(map(res149.next)) | } 20000 30000 49999 scala> for(e<-map.values) | println(e) 20000 30000 49999 |
通过以上方法可以直接遍历key或者value
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scala> for(e<-map){ | println(e) | } (zhangsan,20000) (lisi,30000) (wangwu,49999) scala> for((x,y)<-map) | println(x,y) (zhangsan,20000) (lisi,30000) (wangwu,49999) scala> for((x,y)<-map) | println(x) zhangsan lisi wangwu scala> for((x,_)<-map) | println(x) zhangsan lisi wangwu scala> for((_,x)<-map) | println(x) 20000 30000 49999 scala> for((_,x)<-map) | println(_) <console>:16: error: missing parameter type for expanded function ((x$1) => println(x$1)) println(_) |
下划线可以统配所有的元素，但是不能取值
toMap方法，可以将一个集合转换为map集合
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scala> var arr = Array("zhangsan"->2000,"lisi"->3000) arr: Array[(String, Int)] = Array((zhangsan,2000), (lisi,3000)) scala> var arr1 = Array(("lisi",3000),("zhaosi",3500)) arr1: Array[(String, Int)] = Array((lisi,3000), (zhaosi,3500)) scala> arr.toMap res158: scala.collection.immutable.Map[String,Int] = Map(zhangsan -> 2000, lisi -> 3000) scala> arr1.toMap res159: scala.collection.immutable.Map[String,Int] = Map(lisi -> 3000, zhaosi -> 3500) scala> var arr = Array(("zhangsan",3000),(1000,20000)) arr: Array[(Any, Int)] = Array((zhangsan,3000), (1000,20000)) scala> arr.toMap res160: scala.collection.immutable.Map[Any,Int] = Map(zhangsan -> 3000, 1000 -> 20000) scala> var map = Map("1"->2,"2"->3,4->"") map: scala.collection.immutable.Map[Any,Any] = Map(1 -> 2, 2 -> 3, 4 -> "") |
toMap的时候，原来的数据一定是一个装有对偶元组的集合
set集合
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scala> var set = Set(1,2,3,4,5) set: scala.collection.immutable.Set[Int] = Set(5, 1, 2, 3, 4) scala> var set = new Set[Int](3) <console>:13: error: trait Set is abstract; cannot be instantiated var set = new Set[Int](3) ^ scala> var set = new HashSet[Int](3) <console>:13: error: not found: type HashSet var set = new HashSet[Int](3) ^ scala> var set = new scala.collection.immutable.HashSet[Int](3) <console>:13: error: too many arguments for constructor HashSet: ()scala.collection.immutable.HashSet[Int] var set = new scala.collection.immutable.HashSet[Int](3) ^ scala> var set = new scala.collection.immutable.HashSet[Int]() set: scala.collection.immutable.HashSet[Int] = Set() scala> set+=1 scala> set res162: scala.collection.immutable.HashSet[Int] = Set(1) scala> var set = Set(1,2,3) set: scala.collection.immutable.Set[Int] = Set(1, 2, 3) scala> set+=12345 scala> set res164: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 12345) |
元素可变，集合长度可变
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cala> var set = scala.collection.mutable.Set(1,2,3,4) set: scala.collection.mutable.Set[Int] = Set(1, 2, 3, 4) scala> set+=123 res169: scala.collection.mutable.Set[Int] = Set(1, 2, 3, 123, 4) scala> set res170: scala.collection.mutable.Set[Int] = Set(1, 2, 3, 123, 4) scala> set-=(1,2,3) res171: scala.collection.mutable.Set[Int] = Set(123, 4) scala> set.insert(1,2) <console>:15: error: value insert is not a member of scala.collection.mutable.Set[Int] set.insert(1,2) ^ scala> set.remove(1) res173: Boolean = false scala> set res174: scala.collection.mutable.Set[Int] = Set(123, 4) scala> set.remove(4) res175: Boolean = true scala> set res176: scala.collection.mutable.Set[Int] = Set(123) |
可变的set集合中存在remove += ++= -= --=
不存在insert ，一般我们使用set都只是为了一个功能去重toSet方法
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scala> var arr = Array(1,2,1,1,1,2,3,4,5) arr: Array[Int] = Array(1, 2, 1, 1, 1, 2, 3, 4, 5) scala> arr.distinct res178: Array[Int] = Array(1, 2, 3, 4, 5) scala> arr.toSet res179: scala.collection.immutable.Set[Int] = Set(5, 1, 2, 3, 4) |
list集合补充
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scala> 1::list res184: List[Int] = List(1, 1, 2, 3) scala> list res185: List[Int] = List(1, 2, 3) scala> list:::list res186: List[Int] = List(1, 2, 3, 1, 2, 3) scala> res186.tail res187: List[Int] = List(2, 3, 1, 2, 3) scala> res186.head res188: Int = 1 |
：：是在一个list上面拼接一个元素，但是元素只能放在前面
：：：拼接的是一个集合List:::List
list的组成方式永远分为两个部分，头元素和尾列表
新拼接的元素就是头元素，后面都是尾列表