目录
Scala简介
- Scala源自Java
Scala构建在JVM之上
Scala与Java兼容、互通 - Scala的优势
多范式编程：面向对象编程、函数式编程
表达能力强、代码精简 - 大数据与Scala
Spark采用Scala语言设计- 提供的API更加优雅
基于JVM的语言更融入Hadoop生态圈
- 提供的API更加优雅
安装scala
#################### 安装Scala ######################
安装Scala，版本要和idea相同
https://www.scala-lang.org/download
要求JDK环境
idea中配置scala，安装包放进idea中
scala开发环境
启用装好的scala编译器
选择与idea版本对应的scala的解压包
新建项目中出现scala说明安装成功
scala交互式编程
cmd
color f0
1+1
res0+12
main方法写对象里，对象object
args:Array[String] 参数
Unit= 返回值类型
public static void main(String []args){}
def main(args:Array[String]):Unit={}
scala初体验
scala> object MyHello{
| def main(args:Array[String]):Unit={
| println("Hello,world");
| }
| }
MyHello.main(null)
Hello,world
Scala概述
- 面向对象特征
每个值都是对象
对象的数据类型和行为由类（class）和特征（Trait，类似于interface）描述
利用特征实现混入式多重继承 - 函数式编程
每个函数都是一个值
支持高阶函数、柯里化（currying）、样例化（case class）及模式匹配… - scala是静态类型语言
- 扩展性
Scala变量与常量
变量
复制后可以改变，生命周期中可以被多次赋值
var 变量名称:类型=xxx
定义变量：var c=20 c: Int = 20
var c="abc" c: String = abc
c=40
<console>:15: error: type mismatch;
found : Int(40)
required: String
c=40
c="40" c: String = 40
一般无需显示指定类型，Scala编译器会自动推断出类型
常量
val 常量名称:类型=xxx
val k=50 k: Int = 50
k=60
<console>:15: error: reassignment to val
k=60
错，常量不可更改
k res16: Int = 50
类型别名
type关键字
type 类型别名=类型
type T=String defined type alias T
val name:T="jason" name: T = jason
Scala数据类型
Scala与Java有着相同的原始数据类型
Scala数据类型层次结构
Any：所有类型的超类（顶级类型）
AnyVal：表示值类型的超类
AnyRef：表示引用类型的超类，对应java.lang.Object
Unit：表示无值，类似于Java中的void
Nothing：所有类型的子类
Null：表示null或空引用
Scala循环控制
while
scala> var num:Int=0;
num: Int = 0
scala> while(num<100){
| print(num+" ");
| num=num+1;
| }
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
scala>
do…while
scala> var num:Int=0;
num: Int = 0
scala> do {
| print(num+" ");
| num=num+5;
| }while(num<200);
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195
scala>
for循环
“i to j”或者"i until j"均表示创建一个区间Range
to前后都含
scala> var i=0;
i: Int = 0
scala> for(i:Int <- 0 to 10) {
| print(i+" ");
| }
0 1 2 3 4 5 6 7 8 9 10
until前含后不含
scala> var i=0;
i: Int = 0
scala> for(i:Int <- 0 until 10) {
| print(i+" ");
| }
0 1 2 3 4 5 6 7 8 9
中断
break
scala> import util.control.Breaks._
import util.control.Breaks._
scala> for (k:Int <- 1 to 10) {
| if(k==5) {
| break;
| }
| print(k+" ");
| }
1 2 3 4 scala.util.control.BreakControl
跳breakable方法实现continue
scala> import util.control.Breaks._
import util.control.Breaks._
scala> for(k:Int <- 1 to 10) {
| breakable {
| if(k==5) {
| break;
| }
| print(k+" ");
| }
| }
1 2 3 4 6 7 8 9 10
for循环过滤
val num=10;
scala> for(i:Int <- 1 to num;if i%2==0;if i>5) {
| println(i*100);
| }
600
800
1000
for循环返回值
for循环中的yield会把当前的元素记下来，保存在集合中，循环结束后将返回该集合
scala> var arr=for(k:Int <- 1 to 10) yield k;
arr: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
scala> for(a <- arr) {
| print(a+" ");
| }
1 2 3 4 5 6 7 8 9 10
// 遍历
scala> for(a:Int <- arr) {
| print(a+" ");
| }
1 2 3 4 5 6 7 8 9 10
使用scala语句实现
0+6=6
1+5=6
2+4=6
3+3=6
4+2=6
5+1=6
6+0=6
scala> for(i:Int <- 0 to 6) {
| println(i + "+" + (6-i) + "=" + 6);
| }
0+6=6
1+5=6
2+4=6
3+3=6
4+2=6
5+1=6
6+0=6
// 输出
*
**
scala> var star="*";
star: String = *
scala> for(k:Int <- 1 to 5) {
| println(star);
| star += "*";
| }
*
**
***
****
*****
Scala数组
存储固定大小的元素
数组索引从0开始
泛型使用方括号
数据元素访问使用圆括号
调用Array的伴生对象中的apply()返回Array实例
//数组创建方式一
scala> var al:Array[String] = new Array[String](3);
al: Array[String] = Array(null, null, null)
scala> al(0)="Jason";
scala> al(1)="Marie";
scala> al(2)="Jimmy";
scala> for(a <- al) {
| print(a+",");
| }
Jason,Marie,Jimmy
scala>
//数组创建方式二
scala> var a2=Array("Jason","Marie","Jimmy");
a2: Array[String] = Array(Jason, Marie, Jimmy)
//数据创建方式三：区间数组
1-10表示范围，2表示步长
scala> var a3=Array.range(1,10,2);
a3: Array[Int] = Array(1, 3, 5, 7, 9)
Scala元组
可以包含不同类型的元素
最多支持22个元素（Tuple1~Tuple22）
使用下划线“_”访问元素，“_1”表示第一个元素
// 元祖声明方式一
scala> var tp1=("Mike","123 ABC street",58)
tp1: (String, String, Int) = (Mike,123 ABC street,58)
scala> println(tp1._1);
Mike
scala> println(tp1._2);
123 ABC street
//迭代元组
scala> tp1.productIterator.foreach{i=>println("Value="+i)}
Value=Mike
Value=123 ABC street
Value=58
//元组声明方式二
scala> var tp2=new Tuple3("Mike","123 ABC street",58);
tp2: (String, String, Int) = (Mike,123 ABC street,58)
//元组声明方式三
scala> def mike="Mike"->5
mike: (String, Int)
//输出scala.Tuple2
scala> mike.getClass
res42: Class[_ <: (String, Int)] = class scala.Tuple2
//将元组元素依次赋给三个变量
scala> val(name,address,age)=tp1
name: String = Mike
address: String = 123 ABC street
age: Int = 58
scala> println(name)
Mike
scala> println(address)
123 ABC street
// 二元元祖:对wordcount比较有用
scala> val k="eee"->5
k: (String, Int) = (eee,5)
// 嵌套二元元祖
scala> val k="eee"->5->6
k: ((String, Int), Int) = ((eee,5),6)
// 只要结构一样，就能取出对应值 解构语法
scala> val ((a,b),c) = k
a: String = eee
b: Int = 5
c: Int = 6
元祖的函数
scala> val tp1 =("zhangsan","ls",50,12.5);
tp1: (String, String, Int, Double) = (zhangsan,ls,50,12.5)
scala> tp1.productIterator.foreach{i=>println(i)}
zhangsan
ls
50
12.5
scala> tp1.
_1 _3 canEqual equals productArity productIterator toString
_2 _4 copy hashCode productElement productPrefix
scala> tp1.productIterator.
++ corresponds foldRight max reduceLeft span toSeq
/: count forall maxBy reduceLeftOption sum toSet
:\ drop foreach min reduceOption take toStream
GroupedIterator dropWhile grouped minBy reduceRight takeWhile toString
addString duplicate hasDefiniteSize mkString reduceRightOption to toTraversable
aggregate exists hasNext next sameElements toArray toVector
buffered filter indexOf nonEmpty scanLeft toBuffer withFilter
collect filterNot indexWhere padTo scanRight toIndexedSeq zip
collectFirst find isEmpty partition seq toIterable zipAll
contains flatMap isTraversableAgain patch size toIterator zipWithIndex
copyToArray fold length product slice toList
copyToBuffer foldLeft map reduce sliding toMap
Scala集合
Seq：序列，元素按顺序排列
Set：集合，元素不重复
Map：映射，键值对集合
不可变集合
scala.clooection.immutable，默认Scala选择不可变集合
可变集合
可以修改、添加、或移除一个集合的元素
scala.collection.mutable
带buffer的都是可变的
常用集合
数组和集合的函数
scala> val arr = Array(1,2,3,4,5,6)
arr: Array[Int] = Array(1, 2, 3, 4, 5, 6)
scala> arr.
++ count hasDefiniteSize maxBy sameElements toBuffer
++: deep head min scan toIndexedSeq
+: diff headOption minBy scanLeft toIterable
/: distinct indexOf mkString scanRight toIterator
:+ drop indexOfSlice nonEmpty segmentLength toList
:\ dropRight indexWhere orElse seq toMap
addString dropWhile indices padTo size toSeq
aggregate elemManifest init par slice toSet
andThen elemTag inits partition sliding toStream
apply endsWith intersect patch sortBy toTraversable
applyOrElse exists isDefinedAt permutations sortWith toVector
array filter isEmpty prefixLength sorted transform
canEqual filterNot isTraversableAgain product span transpose
clone find iterator reduce splitAt union
collect flatMap last reduceLeft startsWith unzip
collectFirst flatten lastIndexOf reduceLeftOption stringPrefix unzip3
combinations fold lastIndexOfSlice reduceOption sum update
companion foldLeft lastIndexWhere reduceRight tail updated
compose foldRight lastOption reduceRightOption tails view
contains forall length repr take withFilter
containsSlice foreach lengthCompare reverse takeRight zip
copyToArray genericBuilder lift reverseIterator takeWhile zipAll
copyToBuffer groupBy map reverseMap to zipWithIndex
corresponds grouped max runWith toArray
scala> var c = Array(2,3,4,67,88)
c: Array[Int] = Array(2, 3, 4, 67, 88)
scala> c ++ arr
res0: Array[Int] = Array(2, 3, 4, 67, 88, 1, 2, 3, 4, 5, 6)
scala> val a = List(3,4,5)
a: List[Int] = List(3, 4, 5)
// 取决于后面的数据类型
scala> a ++: arr
res1: Array[Int] = Array(3, 4, 5, 1, 2, 3, 4, 5, 6)
scala> var k = 100
k: Int = 100
scala> k +: arr
res2: Array[Int] = Array(100, 1, 2, 3, 4, 5, 6)
scala> arr :+ k
res3: Array[Int] = Array(1, 2, 3, 4, 5, 6, 100)
// 数据类型取决于：的方向
scala> k +: a
res5: List[Int] = List(100, 3, 4, 5)
// a当成方法来加
scala> c.++(a)
res6: Array[Int] = Array(2, 3, 4, 67, 88, 3, 4, 5)
scala> k
res7: Int = 100
scala> a
res8: List[Int] = List(3, 4, 5)
// ：方向代表集合的方向
scala> (100 /: a)(_+_)
res9: Int = 112
scala> (a :\ 100)(_+_)
res11: Int = 112
// 建立一个空字符串
scala> var str = new StringBuilder
str: StringBuilder =
scala> a.addString(str)
res12: StringBuilder = 345
scala> str
res13: StringBuilder = 345
scala> a.addString(str,"#")
res15: StringBuilder = 3453#4#5
scala> var str = ""
str: String = ""
scala> var str = new StringBuilder
str: StringBuilder =
scala> a.addString(str,"[",",","]")
res16: StringBuilder = [3,4,5]
addString用java来表示
public String addString(List lst, String start, String flag, String end) {
StringBuffer sb = new StringBuffer();
sb.append(start);
for (Object o : lst) {
sb.append(o+flag);
}
Pattern p = Pattern.compile(flag + "$");
sb.append(end);
sb = new StringBuffer(sb.toString().replaceFirst(flag+"$",""));
return sb.toString();
}
public static void main(String[] args) {
App app = new App();
List lst = new ArrayList();
lst.add(34);
lst.add(23);
lst.add(44);
lst.add(5);
lst.add("sdf");
System.out.println(app.addString(lst,"[",",","]")); // [34,23,44,5,sdf,]
// par并行集合，集合分散到多个节点上 scala并行集合 分治算法
在这里插入代码片scala> val c = Array(2,3,4,56,76,43,58)
c: Array[Int] = Array(2, 3, 4, 56, 76, 43, 58)
scala> val d = Array(2,3,45,5)
d: Array[Int] = Array(2, 3, 45, 5)
// canEqual是否可以相比 数组：万物皆可比
scala> c.canEqual(d)
res0: Boolean = true
scala> c.canEqual("aa")
res1: Boolean = true
scala> c.canEqual('z')
res2: Boolean = true
scala> object myObj{} 对象
defined object myObj
scala> c.canEqual(myObj)
res3: Boolean = true
scala> e.charAt(2)
res5: Char = c
scala> var e = Array('a','b','c')
e: Array[Char] = Array(a, b, c)
// 把c的指针同时指向e
scala> var e = c
e: Array[Int] = Array(2, 3, 4, 56, 76, 43, 58)
scala> c
res6: Array[Int] = Array(2, 3, 4, 56, 76, 43, 58)
scala> c(2)=44
scala> c
res8: Array[Int] = Array(2, 3, 44, 56, 76, 43, 58)
scala> e
res9: Array[Int] = Array(2, 3, 44, 56, 76, 43, 58)
// clone相当于复制
scala> var k = c.clone
k: Array[Int] = Array(2, 3, 44, 56, 76, 43, 58)
scala> c(2)=100
scala> c
res11: Array[Int] = Array(2, 3, 100, 56, 76, 43, 58)
scala> k
res12: Array[Int] = Array(2, 3, 44, 56, 76, 43, 58)
scala> var fun:PartialFunction[Int,Int]={
| case x => x+1
| }
fun: PartialFunction[Int,Int] = <function1>
scala> c.collect(fun)
res13: Array[Int] = Array(3, 4, 101, 57, 77, 44, 59)
scala> var fun:PartialFunction[Int,Int]={
| case 3 => 13
| }
fun: PartialFunction[Int,Int] = <function1>
scala> c.collect(fun)
res14: Array[Int] = Array(13)
// 偏函数:对不同的部分采用不同的处理方式
scala> val fun:PartialFunction[Int,Int]={
| case 3 => 13
| case y if y%2==0 => y+50
| case x => x
| }
fun: PartialFunction[Int,Int] = <function1>
scala> c.collect(fun)
res15: Array[Int] = Array(52, 13, 150, 106, 126, 43, 108)
scala> val fun:PartialFunction[Int,String]={
| case 3 => "xixi"
| case y if y%2==0 => "gg"
| case x => x+"ff"
| }
fun: PartialFunction[Int,String] = <function1>
scala> c.collect(fun)
res16: Array[String] = Array(gg, xixi, gg, gg, gg, 43ff, gg)
scala> c.combinations(3)
res17: Iterator[Array[Int]] = non-empty iterator // 迭代器就是一个指针，只能迭代一遍
scala> c
res18: Array[Int] = Array(2, 3, 100, 56, 76, 43, 58)
scala> var ee = c.combinations(3)
ee: Iterator[Array[Int]] = non-empty iterator ^
scala> ee.foreach(x=>println(x))
[I@4865434e
[I@3c6e407
[I@287dde94
[I@2f650dae
[I@4df8443f
[I@79aa675b
[I@3fe59f84
[I@38eafdab
[I@373c8f35
[I@1d86b636
[I@e0c03bd
[I@61e4a072
[I@32f2de5c
[I@1a6df932
[I@74120029
[I@3031d9e9
[I@1415f18d
[I@61c42e54
[I@533690d
[I@3bf306d3
[I@5101b9
[I@40273969
[I@5ec25b61
[I@7da40bf4
[I@75708130
[I@c651286
[I@40304938
[I@1d160161
[I@6c9e7af2
[I@48cbb4c5
[I@af04d6d
[I@2740585b
[I@3816efab
[I@2d6e09f0
[I@257da215
scala> var ee = c.combinations(3)
ee: Iterator[Array[Int]] = non-empty iterator
scala> ee.foreach(x=>println(x.mkString(",")))
2,3,100
2,3,56
2,3,76
2,3,43
2,3,58
2,100,56
2,100,76
2,100,43
2,100,58
2,56,76
2,56,43
2,56,58
2,76,43
2,76,58
2,43,58
3,100,56
3,100,76
3,100,43
3,100,58
3,56,76
3,56,43
3,56,58
3,76,43
3,76,58
3,43,58
100,56,76
100,56,43
100,56,58
100,76,43
100,76,58
100,43,58
56,76,43
56,76,58
56,43,58
76,43,58
// 是否包含元素
scala> c.contains(50)
res23: Boolean = false
scala> c.contains(2)
res24: Boolean = true
scala> var d = Array(23,34,50)
d: Array[Int] = Array(23, 34, 50)
// 是否包含数组
scala> c.containsSlice(d)
res25: Boolean = false
// drop丢弃元素
scala> d.drop(2)
res26: Array[Int] = Array(50)
scala> d
res27: Array[Int] = Array(23, 34, 50)
scala> d.dropRight(2)
res28: Array[Int] = Array(23)
scala> d
res29: Array[Int] = Array(23, 34, 50)
scala> val a =Array(0,0,0,0,0,0,0)
a: Array[Int] = Array(0, 0, 0, 0, 0, 0, 0)
scala> c
res31: Array[Int] = Array(2, 3, 100, 56, 76, 43, 58)
scala> a
res32: Array[Int] = Array(0, 0, 0, 0, 0, 0, 0)
// 把c拷贝到a，从a的第二个位置开始考
scala> c.copyToArray(a,2)
scala> a
res34: Array[Int] = Array(0, 0, 2, 3, 100, 56, 76)
scala> import scala.
#:: Product14
+: Product15
:+ Product16
:: Product17
AbstractMethodError Product18
Any Product19
AnyRef Product2
AnyVal Product20
AnyValCompanion Product21
App Product22
Array Product3
ArrayIndexOutOfBoundsException Product4
BigDecimal Product5
BigInt Product6
Boolean Product7
BufferedIterator Product8
Byte Product9
Char Proxy
ClassCastException Range
Cloneable Responder
Console Right
DelayedInit RuntimeException
DeprecatedConsole ScalaReflectionException
DeprecatedPredef Seq
Double SerialVersionUID
Dynamic Serializable
Either Short
Enumeration Singleton
Equals Some
Equiv Specializable
Error Stream
Exception StringBuilder
FallbackArrayBuilding StringContext
Float StringIndexOutOfBoundsException
Fractional Symbol
Function Throwable
Function0 Traversable
Function1 TraversableOnce
Function10 Tuple1
Function11 Tuple10
Function12 Tuple11
Function13 Tuple12
Function14 Tuple13
Function15 Tuple14
Function16 Tuple15
Function17 Tuple16
Function18 Tuple17
Function19 Tuple18
Function2 Tuple19
Function20 Tuple2
Function21 Tuple20
Function22 Tuple21
Function3 Tuple22
Function4 Tuple3
Function5 Tuple4
Function6 Tuple5
Function7 Tuple6
Function8 Tuple7
Function9 Tuple8
IllegalArgumentException Tuple9
Immutable UninitializedError
IndexOutOfBoundsException UninitializedFieldError
IndexedSeq UniquenessCache
Int Unit
Integral UnsupportedOperationException
InterruptedException Vector
Iterable actors
Iterator annotation
Left beans
List collection
Long compat
LowPriorityImplicits concurrent
MatchError deprecated
Mutable deprecatedName
Nil inline
NoSuchElementException io
None language
NotImplementedError languageFeature
NotNull math
Nothing native
Null noinline
NullPointerException package
NumberFormatException ref
Numeric reflect
Option remote
Ordered runtime
Ordering specialized
PartialFunction swing
PartialOrdering sys
PartiallyOrdered text
Predef throws
Product tools
Product1 transient
Product10 unchecked
Product11 util
Product12 volatile
Product13 xml
scala> import scala.util.
DynamicVariable MurmurHash Right continuations parsing
Either Properties Sorting control
Failure PropertiesTrait Success hashing
Left Random Try matching
scala> import scala.collection.mutable.Array
ArrayBuffer ArrayBuilder ArrayLike ArrayOps ArraySeq ArrayStack
scala> import scala.collection.mutable.ArrayBu
ArrayBuffer ArrayBuilder
scala> import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.ArrayBuffer
scala> var a:ArrayBuffer[Int] = ArrayBuffer()
a: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()
scala> var a:ArrayBuffer[Int] = ArrayBuffer()
a: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()
scala> c.copyToBuffer(a)
scala> a
res37: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 3, 100, 56, 76, 43, 58)
// 比较两者是否相同
scala> c.corresponds(a)(_==_)
res38: Boolean = true
scala> a.re
readOnly reduceLeftOption reduceRightOption repr reverseIterator
reduce reduceOption reduceToSize result reverseMap
reduceLeft reduceRight remove reverse
scala> a.remove(3)
res39: Int = 56
scala> a
res40: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 3, 100, 76, 43, 58)
scala> c.corresponds(a)(_==_)
res41: Boolean = false
// 统计偶数个数
scala> c.count(p=>p%2==0)
res42: Int = 5
scala> c:+23
res46: Array[Int] = Array(2, 3, 100, 56, 76, 43, 58, 23)
scala> c
res43: Array[Int] = Array(2, 3, 100, 56, 76, 43, 58)
scala> var c =Array(2,3,100,56,76,42,58)
c: Array[Int] = Array(2, 3, 100, 56, 76, 42, 58)
scala> c=c:+2
c: Array[Int] = [I@261b4fa
scala> c.distinct
res49: Array[Int] = Array(2, 3, 100, 56, 76, 42, 58)
scala> c.drop
drop dropRight dropWhile
scala> c.dropWhile(p=>p%2==0)
res50: Array[Int] = Array(3, 100, 56, 76, 42, 58, 2)
scala> a
res51: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 3, 100, 76, 43, 58)
scala> a.drop
drop dropRight dropWhile
scala> a.dropWhile(p=>p%2==0)
res52: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(3, 100, 76, 43, 58)
// 删除直到碰到第一个不满足条件的元素为止
scala> val a =Array(3,2,3,4)
a: Array[Int] = Array(3, 2, 3, 4)
scala> val c = a.dropWhile({x:Int => x>2})
c: Array[Int] = Array(2, 3, 4)
scala> println(c.mkString(","))
2,3,4
scala> val c = Array(2,3,4)
c: Array[Int] = Array(2, 3, 4)
scala> a
res56: Array[Int] = Array(3, 2, 3, 4)
// a是否以c结尾
scala> a.endsWith(c)
res54: Boolean = true
scala> a.st
startsWith stringPrefix
// a是否以c开头
scala> a.startsWith(c)
res55: Boolean = false
// a里元素是否存在大于5的
scala> a.exists(p=>p>5)
res57: Boolean = false
// 过滤
scala> a.filter
filter filterNot
scala> a.filter(p=>p%2==0) 过滤偶数
res58: Array[Int] = Array(2, 4)
// 判断是否为偶数的函数
scala> def myfun(p:Int):Boolean={
| p%2==0
| }
myfun: (p: Int)Boolean
scala> a.filter(myfun) // 函数作为参数传递给另一个函数：高阶函数
res60: Array[Int] = Array(2, 4)
scala> a.filterNot(myfun) // 反过滤
res61: Array[Int] = Array(3, 3)
scala> a.find(x=>x==2)
res62: Option[Int] = Some(2) // 返回some类型的数组 代表找到了之后放入some数组里
scala> a.find(x=>x==2).g
genericBuilder get getClass getOrElse groupBy grouped
scala> a.find(x=>x==2).get // some类型拿取的方法是get
res63: Int = 2
scala> val c = Array(4,5,6)
c: Array[Int] = Array(4, 5, 6)
scala> c.flat
flatMap flatten
scala> c.map(x=>(1 to x)) 返回从1到x的数组
res65: Array[scala.collection.immutable.Range.Inclusive]
= Array(Range(1, 2, 3, 4), Range(1, 2, 3, 4, 5), Range(1, 2, 3, 4, 5, 6))
scala> c.map(x=>(1 to x)).flatten
res66: Array[Int] = Array(1, 2, 3, 4, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6)
scala> c.flatMap(x=>(1 to x)) // flatMap = flatten（扁平化）+map 返回两层数组 先map再flatten
res64: Array[Int] = Array(1, 2, 3, 4, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6) // 扁平化
柯里化：把接受多个参数变成接受单个参数的函数链
public void eee(String s,String y)...
def eee(s:String)(y:String)...
var ee = function(k){alert(k);}
var ff = function(fun){return fun;}
ff(ee)(10); => 10 // 柯里化
scala> c
res67: Array[Int] = Array(4, 5, 6)
scala> c.fold(5)(_+_)
res68: Int = 20
scala> def nyfun(m:Int,n:Int):Int = {
| m+n
| }
nyfun: (m: Int, n: Int)Int
scala> c.fold(5)(nyfun)
res69: Int = 20
scala> val a = Array(1,2,3,4)
a: Array[Int] = Array(1, 2, 3, 4)
scala> def seqno(m:Int,n:Int): Int ={
| val s = "seq_exp=%d+%d"
| println(s.format(m,n))
| return m+n
| }
seqno: (m: Int, n: Int)Int
scala> def combine(m:Int,n:Int): Int ={
| val s = "com_exp=%d+%d"
| println(s.format(m,n))
| return m+n
| }
combine: (m: Int, n: Int)Int
scala> val b = a.fold(5)(seqno)
seq_exp=5+1
seq_exp=6+2
seq_exp=8+3
seq_exp=11+4
b: Int = 15
scala> val c = a.par.aggregate(5)(seqno,combine)
seq_exp=5+3
seq_exp=5+4
seq_exp=5+2
seq_exp=5+1
com_exp=6+7
com_exp=8+9
com_exp=13+17
c: Int = 30
scala> val c = a.par.aggregate(5)(seqno,combine)
seq_exp=5+1
seq_exp=5+3
seq_exp=5+4
seq_exp=5+2
com_exp=8+9
com_exp=6+7
com_exp=13+17
c: Int = 30
scala> val c = a.par.aggregate(5)(seqno,combine)
seq_exp=5+1
seq_exp=5+3
seq_exp=5+4
seq_exp=5+2
com_exp=8+9
com_exp=6+7
com_exp=13+17
c: Int = 30
scala> val k =Array(34,55,776,8,67)
k: Array[Int] = Array(34, 55, 776, 8, 67)
scala> var a = 21
a: Int = 21
scala> var a = Array(1,2,3)
a: Array[Int] = Array(1, 2, 3)
scala> k.g
genericBuilder getClass groupBy grouped
scala> k.group
groupBy grouped
// 奇偶数分组
scala> k.groupBy(x=> x match {
| case x if x%2==0 => "ou"
| case _ => "ji"
| })
res71: scala.collection.immutable.Map[String,Array[Int]]
= Map(ou -> Array(34, 776, 8), ji -> Array(55, 67))
scala> k.grouped(3)
res72: Iterator[Array[Int]] = non-empty iterator
scala> k.grouped(3).foreach(x=>println(x))
[I@6c2ff925
[I@7985c7ed
scala> k.grouped(3).foreach(x=>println(x.mkString(",")))
34,55,776
8,67
scala> k.head // 返回序列中的第一个元素
res75: Int = 34
scala> k.tail // 返回去头
res76: Array[Int] = Array(55, 776, 8, 67)
scala> k.last
res77: Int = 67
scala> var lst = ArrayBuffer()
lst: scala.collection.mutable.ArrayBuffer[Nothing] = ArrayBuffer()
scala> lst.headOption
res80: Option[Nothing] = None
scala> val a = (1 to 20)
a: scala.collection.immutable.Range.Inclusive = Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
scala> a.indexOfSlice((4 to 6)) // 返回下标
res81: Int = 3
scala> a.indexWhere(p=>p>10)
res82: Int = 10
scala> a.init // 去尾
res83: scala.collection.immutable.Range = Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
// 依次做init操作,直至为空
scala> val a = Array(1,2,3,4,5)
a: Array[Int] = Array(1, 2, 3, 4, 5)
scala> val b = a.inits.toList
b: List[Array[Int]] = List(Array(1, 2, 3, 4, 5), Array(1, 2, 3, 4), Array(1, 2, 3), Array(1, 2), Array(1), Array())
scala> for(i <- 1 to b.length) {
| val s = "第%d个值：%s"
| println(s.format(i,b(i-1).mkString(",")))
| }
第1个值：1,2,3,4,5
第2个值：1,2,3,4
第3个值：1,2,3
第4个值：1,2
第5个值：1
第6个值：
// 取两个集合的交集
scala> val a =Array(1,2,2,3,4,5)
a: Array[Int] = Array(1, 2, 2, 3, 4, 5)
scala> val b = Array(3,4,5)
b: Array[Int] = Array(3, 4, 5)
scala> val c = a.intersect(b)
c: Array[Int] = Array(3, 4, 5)
// 判断是否有20这个下标
scala> b.isDefinedAt(20)
res85: Boolean = false
scala> b.isDefinedAt(20)
res85: Boolean = false
scala> b.isEmpty
res86: Boolean = false
scala> import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.ArrayBuffer
scala> var c = ArrayBuffer()
c: scala.collection.mutable.ArrayBuffer[Nothing] = ArrayBuffer()
scala> c.isEmpty
res87: Boolean = true
// 判断序列是否可以反复遍历，迭代器不可以反复遍历 isTraversableAgain
scala> val arr = Array(1,345,65,787,98)
arr: Array[Int] = Array(1, 345, 65, 787, 98)
scala> arr.isTraversableAgain
res57: Boolean = true
scala> arr.inits.isTraversableAgain
res58: Boolean = false
scala> arr.iterator
res59: Iterator[Int] = non-empty iterator
scala> arr.iterator.isTraversableAgain
res60: Boolean = false
// 迭代器的foreach方法,只有collection的集合才有迭代器
public static void main(String[] args){
List lst = new ArrayList();
lst.add(34);
lst.add(24);
lst.add(5);
lst.add(44);
lst.add("sdf");
for(Iterator iterator = lst.iterator();iterator.hasNext();){
sou(iterator.next());
}
}
// lengthCompare比较数组长度和给定的值的差
scala> arr.lengthCompare(3)
res61: Int = 2
scala> arr.lengthCompare(2)
res62: Int = 3
scala> arr.lengthCompare(7)
res63: Int = -2
scala> arr.lengthCompare(6)
res64: Int = -1
scala> arr.lengthCompare(5)
res65: Int = 0
// 单词计数出现的次数
scala> val str = "hello mysql hello world"
str: String = hello mysql hello world
scala> str.split(" ")
res67: Array[String] = Array(hello, mysql, hello, world)
scala> str.split(" ").map(x => (x,1))
res68: Array[(String, Int)] = Array((hello,1), (mysql,1), (hello,1), (world,1)) // 元组类型的数组
// 按数组里元组的第一个元素即单词分组
scala> str.split(" ").map(x => (x,1)).groupBy(x => x._1)
// world是键，Array((world,1))是值，值是数组，数组的长度就是出现的次数
res69: scala.collection.immutable.Map[String,Array[(String, Int)]] =
Map(world -> Array((world,1)), mysql -> Array((mysql,1)), hello -> Array((hello,1), (hello,1)))
scala> str.split(" ").map(x => (x,1)).groupBy(x => x._1).foreach(x=>{println(x._1,x._2.length)})
(world,1)
(mysql,1)
(hello,2)
scala> str.split(" ").map((_,1)).groupBy(_._1).foreach(x=>{println(x._1,x._2.length)})
(world,1)
(mysql,1)
(hello,2)
// 扁平化集合
scala> val c = List("hello world","hello hadoop","hadoop hive")
c: List[String] = List(hello world, hello hadoop, hadoop hive)
scala> c.map(_.split(" "))
res73: List[Array[String]] = List(Array(hello, world), Array(hello, hadoop), Array(hadoop, hive))
scala> c.map(_.split(" ")).flatten
res74: List[String] = List(hello, world, hello, hadoop, hadoop, hive)
scala> c.flatMap(_.split(" "))
res76: List[String] = List(hello, world, hello, hadoop, hadoop, hive)
// 找序列中的最大最小值，和第一个符合条件的值
scala> arr.max
res78: Int = 787
scala> arr.maxBy(_>456)
res79: Int = 787
scala> arr.min
res80: Int = 1
scala> arr.minBy(_>34)
res81: Int = 1
scala> a
res82: Array[String] = Array(hello, mysql, hello, world)
scala> arr
res83: Array[Int] = Array(1, 345, 65, 787, 98)
scala> arr.minBy(_<1)
res84: Int = 1
scala> arr.nonEmpty
res85: Boolean = true
// 特定位置补位
scala> arr.padTo(10,0) // 补位
res86: Array[Int] = Array(1, 345, 65, 787, 98, 0, 0, 0, 0, 0)
scala> val arr1 = Array(1,2,3)
arr1: Array[Int] = Array(1, 2, 3)
// 批量替换
scala> val a1 = arr.padTo(10,0)
a1: Array[Int] = Array(1, 345, 65, 787, 98, 0, 0, 0, 0, 0)
scala> arr1.copyToArray(a1,5,3)
scala> a1
res88: Array[Int] = Array(1, 345, 65, 787, 98, 1, 2, 3, 0, 0)
scala> arr.partition(_%2 == 0) // 奇偶分区
res89: (Array[Int], Array[Int]) = (Array(98),Array(1, 345, 65, 787))
scala> arr
res90: Array[Int] = Array(1, 345, 65, 787, 98)
scala> arr1
res91: Array[Int] = Array(1, 2, 3)
scala> arr.patch(0,arr1,1) // 批量替换
res92: Array[Int] = Array(1, 2, 3, 345, 65, 787, 98)
// 组合
scala> arr.combinations(3)
res93: Iterator[Array[Int]] = non-empty iterator
scala> arr.combinations(3).foreach(x=>println(x.mkString(",")))
1,345,65
1,345,787
1,345,98
1,65,787
1,65,98
1,787,98
345,65,787
345,65,98
345,787,98
65,787,98
// 排列组合
scala> arr.permutations.toList
res95: List[Array[Int]] = List(Array(1, 345, 65, 787, 98), Array(1, 345, 65, 98, 787), Array(1, 345, 787, 65, 98),
Array(1, 345, 787, 98, 65), Array(1, 345, 98, 65, 787), Array(1, 345, 98, 787, 65), Array(1, 65, 345, 787, 98),
Array(1, 65, 345, 98, 787), Array(1, 65, 787, 345, 98), Array(1, 65, 787, 98, 345), Array(1, 65, 98, 345, 787),
Array(1, 65, 98, 787, 345), Array(1, 787, 345, 65, 98), Array(1, 787, 345, 98, 65), Array(1, 787, 65, 345, 98),
Array(1, 787, 65, 98, 345), Array(1, 787, 98, 345, 65), Array(1, 787, 98, 65, 345), Array(1, 98, 345, 65, 787),
Array(1, 98, 345, 787, 65), Array(1, 98, 65, 345, 787), Array(1, 98, 65, 787, 345), Array(1, 98, 787, 345, 65),
Array(1, 98, 787, 65, 345), Array(345, 1, 65, 787, 98), Array(345, 1, 65, 98, 787), Array(345, 1, 787, 65, 98),
Array(345,...
// 排列组合后的序列长度
scala> arr.permutations.toList.length
res96: Int = 120
scala> arr1
res97: Array[Int] = Array(1, 2, 3)
scala> arr1.permutations
res98: Iterator[Array[Int]] = non-empty iterator
scala> arr1.permutations.toList
res99: List[Array[Int]] = List(Array(1, 2, 3), Array(1, 3, 2), Array(2, 1, 3), Array(2, 3, 1), Array(3, 1, 2), Array(3, 2, 1))
scala> arr1.permutations.to
to toBuffer toIterable toList toSeq toStream toTraversable
toArray toIndexedSeq toIterator toMap toSet toString toVector
scala> arr1.permutations.toSeq
res101: Seq[Array[Int]] = Stream([I@5011663b, ?)
scala> arr1.permutations.toSet
res102: scala.collection.immutable.Set[Array[Int]] = Set(Array(1, 3, 2), Array(1, 2, 3), // 不可改变的
Array(3, 2, 1), Array(2, 1, 3), Array(2, 3, 1), Array(3, 1, 2))
scala> arr.prefixLength(_<787) // 前置小于787
res103: Int = 3
scala> (1 to 5).product // 求积
res104: Int = 120
scala> (1 to 5).sum // 求和
res105: Int = 15
scala> arr.reduce
reduce reduceLeftOption reduceRight
reduceLeft reduceOption reduceRightOption
scala> arr.reduce(_+_) // 求和
res106: Int = 1296
scala> arr.reverse
reverse reverseIterator reverseMap
scala> arr.reverse // 序列反转，java里的StringBuffer
res107: Array[Int] = Array(98, 787, 65, 345, 1)
scala> arr.reverseMap((_,1)) // 反转后作为键放入map
res108: Array[(Int, Int)] = Array((98,1), (787,1), (65,1), (345,1), (1,1))
scala> val arr2 = arr.clone
arr2: Array[Int] = Array(1, 345, 65, 787, 98)
scala> arr.sameElements(arr2) // 比较是否相同
res109: Boolean = true
scala> arr
res110: Array[Int] = Array(1, 345, 65, 787, 98)
// 从第二位开始找找符合<500的连续元素的长度
scala> arr.segmentLength(_<500,1)
res111: Int = 2
scala> arr.seq
res112: scala.collection.mutable.IndexedSeq[Int] = WrappedArray(1, 345, 65, 787, 98)
scala> arr.slice(1,4)
res113: Array[Int] = Array(345, 65, 787)
// 从第一个元素开始，每个元素和它后面的 size - 1 个元素组成一个数组，
// 最终组成一个新的集合返回，当剩余元素不够 size 数，则停止
scala> arr.sliding(3).foreach(x => println(x.mkString(",")))
1,345,65
345,65,787
65,787,98
// 第一次向后跳三位然后再取值，第二个3表示步长
scala> arr.sliding(3,3).foreach(x => println(x.mkString(",")))
1,345,65
787,98
scala> arr.sliding(3,2).foreach(x => println(x.mkString(",")))
1,345,65
65,787,98
scala> arr.sliding(3,4).foreach(x => println(x.mkString(",")))
1,345,65
98
scala> arr.sortBy(x => x) // 默认升序
res118: Array[Int] = Array(1, 65, 98, 345, 787)
scala> arr.sortBy(x => 0-x) // 降序
res119: Array[Int] = Array(787, 345, 98, 65, 1)
scala> val arr = Array("hello","world","are")
arr: Array[String] = Array(hello, world, are)
scala> arr.sortBy(x=> x)
res120: Array[String] = Array(are, hello, world)
scala> var arr1 = arr:+20
arr1: Array[Any] = Array(hello, world, are, 20)
scala> var arr1 = arr:+20:+"abc"
arr1: Array[Any] = Array(hello, world, are, 20, abc)
scala> arr1.sortBy(x => x)
<console>:14: error: No implicit Ordering defined for Any.
arr1.sortBy(x => x)
scala> arr1.map(x=>x+"")
res127: Array[String] = Array(hello, world, are, 20, abc)
scala> arr1.map(x=>x+"").sortWith(_.compareTo(_)>0)
res126: Array[String] = Array(world, hello, are, abc, 20)
scala> def mycomp(x:Any,y:Any):Boolean = {
| x.asInstanceOf[String] > y.asInstanceOf[String]
| }
mycomp: (x: Any, y: Any)Boolean
scala> mycomp("abc",20)
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
at .mycomp(<console>:12)
... 32 elided
scala> def mycomp(x:Any,y:Any):Boolean = {
| x+"" > y+""
| }
mycomp: (x: Any, y: Any)Boolean
scala> mycomp("abc",20)
res129: Boolean = true
scala> arr1.sortWith(mycomp) // 括号里需要函数，函数有两个参数，返回boolean型
res130: Array[Any] = Array(world, hello, are, abc, 20)
scala> def mycomp(x:(Any,Any)):Boolean = {
| x._1+"" > x._2+""
| }
mycomp: (x: (Any, Any))Boolean
scala> mycomp(("abc",20))
res132: Boolean = true
scala> arr1.sortWith(mycomp)
<console>:15: error: type mismatch;
found : ((Any, Any)) => Boolean
required: (Any, Any) => Boolean
arr1.sortWith(mycomp)
^
scala> def mycomp(x:Any,y:Any):Boolean = (x,y) match{
| case (f:String,g:String) => f > g
| case (f:Integer,g:String) => f.toString > g
| case (f:String,g:Integer) => f > g.toString
| case (f:Integer,g:Integer) => f > g
| }
mycomp: (x: Any, y: Any)Boolean
// Any类型无法比较大小
scala> arr1.partition(x => x.isInstanceOf[Int])
res139: (Array[Any], Array[Any]) = (Array(20),Array(hello, world, are, abc))
scala> arr1.splitAt(2)
res144: (Array[Any], Array[Any]) = (Array(hello, world),Array(are, 20, abc))
scala> val t1 = Array("world","are")
t1: Array[String] = Array(world, are)
scala> arr1.startsWith(t1,1)
res147: Boolean = true
scala> val t2 = Array(20,"abc")
t2: Array[Any] = Array(20, abc)
scala> arr1.endsWith(t2)
res152: Boolean = true
stringPrefix返回 toString 结果的前缀
scala> arr1.slice(1,3) // subSequence
res154: Array[Any] = Array(world, are)
scala> arr1.take(3) // 拿前三个元素
res155: Array[Any] = Array(hello, world, are)
scala> arr1.takeWhile(_.isInstanceOf[String])
res158: Array[Any] = Array(hello, world, are)
scala> arr1.toIterator
res159: Iterator[Any] = non-empty iterator
scala> arr1.toList
res160: List[Any] = List(hello, world, are, 20, abc)
scala> arr.toList.
++ flatMap min sortBy
++: flatten minBy sortWith
+: fold mkString sorted
/: foldLeft nonEmpty span
:+ foldRight orElse splitAt
:: forall padTo startsWith
::: foreach par stringPrefix
:\ genericBuilder partition sum
WithFilter groupBy patch tail
addString grouped permutations tails
aggregate hasDefiniteSize prefixLength take
andThen hashCode product takeRight
apply head productArity takeWhile
applyOrElse headOption productElement to
canEqual indexOf productIterator toArray
collect indexOfSlice productPrefix toBuffer
collectFirst indexWhere reduce toIndexedSeq
combinations indices reduceLeft toIterable
companion init reduceLeftOption toIterator
compose inits reduceOption toList
contains intersect reduceRight toMap
containsSlice isDefinedAt reduceRightOption toSeq
copyToArray isEmpty repr toSet
copyToBuffer isTraversableAgain reverse toStream
corresponds iterator reverseIterator toString
count last reverseMap toTraversable
diff lastIndexOf reverse_::: toVector
distinct lastIndexOfSlice runWith transpose
drop lastIndexWhere sameElements union
dropRight lastOption scan unzip
dropWhile length scanLeft unzip3
endsWith lengthCompare scanRight updated
equals lift segmentLength view
exists map seq withFilter
filter mapConserve size zip
filterNot max slice zipAll
find maxBy sliding zipWithIndex
scala> val ar = Array(Array(3,4,5),Array(7,8,9),Array(10,11,12))
ar: Array[Array[Int]] = Array(Array(3, 4, 5), Array(7, 8, 9), Array(10, 11, 12))
scala> ar.transpose // 行转列
res161: Array[Array[Int]] = Array(Array(3, 7, 10), Array(4, 8, 11), Array(5, 9, 12))
union并集
scala> val ar = Array(Array(3,4,5),Array(7,8,9),Array(10,11,12))
ar: Array[Array[Int]] = Array(Array(3, 4, 5), Array(7, 8, 9), Array(10, 11, 12))
scala> ar.transpose
res161: Array[Array[Int]] = Array(Array(3, 7, 10), Array(4, 8, 11), Array(5, 9, 12))
scala> val ar1 = Array(Array(3,4,5),Array(7,8,9))
ar1: Array[Array[Int]] = Array(Array(3, 4, 5), Array(7, 8, 9))
scala> ar1.unzip
<console>:13: error: No implicit view available from Array[Int] => (T1, T2).
ar1.unzip
^
scala> val ar1 = Array((3,4),(7,8)) // 必须数组里元素为元祖，必须2*2
ar1: Array[(Int, Int)] = Array((3,4), (7,8))
scala> ar1.unzip
res163: (Array[Int], Array[Int]) = (Array(3, 7),Array(4, 8))
scala> arr
res164: Array[String] = Array(hello, world, are)
scala> arr1
res165: Array[Any] = Array(hello, world, are, 20, abc)
scala> arr1(3) = 60
scala> arr1
res167: Array[Any] = Array(hello, world, are, 60, abc)
scala> arr1.update(3,80)
scala> arr1
res169: Array[Any] = Array(hello, world, are, 80, abc)
scala> arr1.updated(3,100)
res170: Array[Any] = Array(hello, world, are, 100, abc)
scala> arr1
res171: Array[Any] = Array(hello, world, are, 80, abc)
scala> arr.view(1,3)
res172: scala.collection.mutable.IndexedSeqView[String,Array[String]] = SeqViewS(...)
scala> arr1.view(1,3).foreach(x => println(x))
world
are
scala> t1
res174: Array[String] = Array(world, are)
scala> t2
res175: Array[Any] = Array(20, abc)
scala> t1.zip(t2)
res176: Array[(String, Any)] = Array((world,20), (are,abc))
scala> val t3 = Array(1,2,3,4,5)
t3: Array[Int] = Array(1, 2, 3, 4, 5)
scala> t3.zip(t1)
res177: Array[(Int, String)] = Array((1,world), (2,are))
scala> t3.zipAll(t1,0,3) // t3少就补3，t1少就补0
res178: Array[(Int, Any)] = Array((1,world), (2,are), (3,3), (4,3), (5,3))
scala> t1.zipAll(t3,0,3)
res179: Array[(Any, Int)] = Array((world,1), (are,2), (0,3), (0,4), (0,5))
scala> t3.zipWithIndex // 自动配索引
res180: Array[(Int, Int)] = Array((1,0), (2,1), (3,2), (4,3), (5,4))
scala> arr1.zipWithIndex
res182: Array[(Any, Int)] = Array((hello,0), (world,1), (are,2), (80,3), (abc,4))
scala> arr1.transform(_+"10") // 对每个元素自动处理
res183: scala.collection.mutable.WrappedArray[Any] = WrappedArray(hello10, world10, are10, 8010, abc10)
scala> arr1.toVector
res184: Vector[Any] = Vector(hello10, world10, are10, 8010, abc10)
scala> import scala.collection.mutable.ListBuffer
import scala.collection.mutable.ListBuffer
scala> var e = ListBuffer(1,2,3)
e: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3)
scala> e+=10 // 修改自身
res187: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 10)
scala> e:+10 // 自身不改，返回值修改
res188: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 10, 10)
scala> e
res189: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 10)
scala> e++=ListBuffer(7,8,9) // 后加集合
res190: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 10, 7, 8, 9)
scala> e++=:ListBuffer(6,5) // 自身不改，返回值加上新集合
res193: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 10, 7, 8, 9, 6, 5)
scala> e
res194: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 10, 7, 8, 9)
scala> 100::k
res195: List[Int] = List(100, 1, 2, 3)
scala> k
res196: List[Int] = List(1, 2, 3)
scala> k::100
<console>:14: error: value :: is not a member of Int
k::100
^
scala> k:+100
res198: List[Int] = List(1, 2, 3, 100)
scala> 100+:k
res199: List[Int] = List(100, 1, 2, 3)
scala> k
res200: List[Int] = List(1, 2, 3)
scala> k:::List(3,4,5) // :::两个集合并一起
res201: List[Int] = List(1, 2, 3, 3, 4, 5)
scala> k++:List(3,4,5) // 有:的都是自身不变的
res204: List[Int] = List(1, 2, 3, 3, 4, 5)
scala> k
res205: List[Int] = List(1, 2, 3)
scala> var f = Set(1,2,3) // set不能重复，去重用toset再赚回来
f: scala.collection.immutable.Set[Int] = Set(1, 2, 3)
scala> f+=20
scala> f
res207: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 20)
scala> f+=20
scala> f
res209: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 20)
// 去重
scala> val arr = Array(1,2,3,4,5,4,3)
arr: Array[Int] = Array(1, 2, 3, 4, 5, 4, 3)
scala> arr.toSet.toArray
res210: Array[Int] = Array(5, 1, 2, 3, 4)
scala> arr.distinct
res211: Array[Int] = Array(1, 2, 3, 4, 5)
scala> var e = Set(1,2,3,4)
e: scala.collection.mutable.Set[Int] = Set(1, 2, 3, 4)
scala> var k = Set(4,5,6)
k: scala.collection.mutable.Set[Int] = Set(5, 6, 4)
scala> e & k
res216: scala.collection.mutable.Set[Int] = Set(4)
scala> e | k
res217: scala.collection.mutable.Set[Int] = Set(1, 5, 2, 6, 3, 4)
scala> k &~ e
res218: scala.collection.mutable.Set[Int] = Set(5, 6)
scala> e &~ k
res220: scala.collection.mutable.Set[Int] = Set(1, 2, 3)
scala> arr.grouped(3).toList.foreach(x => println(x.sorted.mkString(",")))
Dwan,Jason,Vince
Lynn,Stephon
scala> arr.grouped(3).toList.foreach(x => println(x.sorted.mkString("List{",",","}")))
List{Dwan,Jason,Vince}
List{Lynn,Stephon}
scala> arr.grouped(3).toList.foreach(x => println(x.sorted)
| )
List(Dwan, Jason, Vince)
List(Lynn, Stephon)
scala> arr.splitAt(3)
res231: (List[String], List[String]) = (List(Jason, Vince, Dwan),List(Lynn, Stephon))
356
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