快学Scala-元祖、集合

1、元祖
映射是K/V对偶的集合，对偶是元组的最简单形式，元组可以装着多个不同类型的值。
1）、创建元祖

//创建元祖时，用小括号那个多个元素括起来，元素之间用逗号隔开，元素的类型可以不一样，元素个数也可以任意多个
scala> val tp = (1,3.3,"scala")
tp: (Int, Double, String) = (1,3.3,scala)

2）、获取元祖的值

scala> tp._1
res37: Int = 1

scala> tp._2
res38: Double = 3.3

scala> tp._3
res39: String = scala

//使用下面这种方式更直观
scala> val t , (a, b, c) = (2, 2.2, "scala")
t: (Int, Double, String) = (2,2.2,scala)
a: Int = 2
b: Double = 2.2
c: String = scala

scala> x
<console>:9: error: not found: value x
              x
              ^

scala> a
res43: Int = 2

scala> b
res44: Double = 2.2

scala> c
res45: String = scala

//对偶元祖加到map中
scala> val m = Map(1 -> "a", 2 -> "b")
m: scala.collection.mutable.Map[Int,String] = Map(2 -> b, 1 -> a)

scala> val t = (3,"c")
t: (Int, String) = (3,c)

scala> m += t
res40: m.type = Map(2 -> b, 1 -> a, 3 -> c)

scala> m
res41: scala.collection.mutable.Map[Int,String] = Map(2 -> b, 1 -> a, 3 -> c)

3）、将对偶集合转换成映射

scala> val arr = Array((1,"a"),(2,"b"))
arr: Array[(Int, String)] = Array((1,a), (2,b))

scala> val t = arr.toMap
t: scala.collection.immutable.Map[Int,String] = Map(1 -> a, 2 -> b)

scala> t
res46: scala.collection.immutable.Map[Int,String] = Map(1 -> a, 2 -> b)

4）、拉链操作
使用zip命令可以将集合中对应的多个值绑定在一起

scala> val arr1 = Array(1,2,3)
arr1: Array[Int] = Array(1, 2, 3)

scala> val arr2 = Array("a","b","c")
arr2: Array[String] = Array(a, b, c)

scala> var arr3 = arr2.zip(arr1)
arr3: Array[(String, Int)] = Array((a,1), (b,2), (c,3))

scala> arr3
res47: Array[(String, Int)] = Array((a,1), (b,2), (c,3))

//如果其中一个元素要多，那么省去最后多余的
//即：如果两个数组的元素个数不一致，拉链操作后生成的数组的长度为较小的那个数组的元素个数
scala> val arr4 = Array("a","b","c","d")
arr4: Array[String] = Array(a, b, c, d)

scala> var arr5 = arr4.zip(arr1)
arr5: Array[(String, Int)] = Array((a,1), (b,2), (c,3))
//arr4中多余的"d"就给省去了
scala> arr5
res49: Array[(String, Int)] = Array((a,1), (b,2), (c,3))

2、集合
Scala的集合有三大类：序列Seq、集Set、映射Map，所有的集合都扩展自Iterable特质（trait）
在Scala中集合有可变（mutable）和不可变（immutable）两种类型，immutable类型的集合初始化后就不能改变了（注意与val修饰的变量进行区别）

1）、序列
可认为java的List

//创建不可变集合
scala> val list = List(1,2,3,4)
list: List[Int] = List(1, 2, 3, 4)

//获取序列中角标为0的元素
scala> list(0)
res50: Int = 1

//由于集合是不可变的所以企图修改其中的值是行不通的
scala> list(0) = 6
<console>:10: error: value update is not a member of List[Int]
              list(0) = 6

//向集合中添加元素生成新的集合
//将0插入到lst1的前面生成一个新的List
scala> val list2 = 0 :: list
list2: List[Int] = List(0, 1, 2, 3, 4)

scala> list2
res52: List[Int] = List(0, 1, 2, 3, 4)

scala> val list3 = list.::(0)
list3: List[Int] = List(0, 1, 2, 3, 4)

scala> val list4 = 0 +: list
list4: List[Int] = List(0, 1, 2, 3, 4)

scala> val list5 = list.+:(0)
list5: List[Int] = List(0, 1, 2, 3, 4)

//将5添加到list最后面
scala> val list6 = list :+ 5
list6: List[Int] = List(1, 2, 3, 4, 5)

//将两个list合并生成一个新的list
scala> list
res57: List[Int] = List(1, 2, 3, 4)

scala> val lst = List(1,5,6,7)
lst: List[Int] = List(1, 5, 6, 7)

scala> val ls = list ++ lst
ls: List[Int] = List(1, 2, 3, 4, 1, 5, 6, 7)

//将lst插入到list前生成一个新的list
scala> val ls2 = lst ++: list
ls2: List[Int] = List(1, 5, 6, 7, 1, 2, 3, 4)

下面是可变序列

//导入可变集合的所有包
scala> import scala.collection.mutable._
import scala.collection.mutable._

//创建可变序列（list）
scala> val lst = ListBuffer[Int]()
lst: scala.collection.mutable.ListBuffer[Int] = ListBuffer()

//直接赋值初始化
scala> val lst2 = ListBuffer(4,5,6,7)
lst2: scala.collection.mutable.ListBuffer[Int] = ListBuffer(4, 5, 6, 7)
//添加元素，以下有两种方式添加元素。注意：没有生成新的集合
scala> lst += 1
res58: lst.type = ListBuffer(1)

scala> lst += 2
res59: lst.type = ListBuffer(1, 2)

scala> lst.app
append        appendAll     apply         applyOrElse

scala> lst.append
append      appendAll

scala> lst.append(3,4)

scala> lst
res61: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 4)

// 将lst2中元素追加到lst中，注意：没有生成新的集合
scala> lst ++= lst2
res62: lst.type = ListBuffer(1, 2, 3, 4, 4, 5, 6, 7)

scala> lst
res63: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 4, 4, 5, 6, 7)

//两个集合合并，生成了新的集合
scala> val lst3 = lst ++ lst2
lst3: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 4, 4, 5, 6, 7, 4, 5, 6, 7)

2）、Set
不可变Set

scala> import scala.collection.immutable._
import scala.collection.immutable._

scala> val s1 = new HashSet[Int]()
s1: scala.collection.immutable.HashSet[Int] = Set()

//将元素1和s1合并生成一个新的set，原有set不变
scala> s1 + 1
res64: scala.collection.immutable.HashSet[Int] = Set(1)

//发现原来的set中还是空
scala> s1
res65: scala.collection.immutable.HashSet[Int] = Set()

scala> res64
res66: scala.collection.immutable.HashSet[Int] = Set(1)

//创建set的时候直接初始化
//重复的元素会去掉
scala> val set1 = Set(1,2,3,3)
set1: scala.collection.immutable.Set[Int] = Set(1, 2, 3)

//两个set相加，生成新的set，重复的元素会自动去掉，且元素排序不是按加入的时候顺序，这样这是set的特性
scala> val set2 = set1 ++ Set(3,4,5)
set2: scala.collection.immutable.Set[Int] = Set(5, 1, 2, 3, 4)

可变set

scala> import scala.collection.mutable._
import scala.collection.mutable._

scala> val set1 = Set(1,2,3,3)
set1: scala.collection.mutable.Set[Int] = Set(1, 2, 3)

//两种方式添加元素，不会生成新的set
scala> set1.add(4)
res69: Boolean = true

scala> set1 += 5
res70: set1.type = Set(1, 5, 2, 3, 4)

scala> set1
res71: scala.collection.mutable.Set[Int] = Set(1, 5, 2, 3, 4)

//删除元素的两种方式
scala> set1 -= 5
res72: set1.type = Set(1, 2, 3, 4)

scala> set1.remove(4)
res73: Boolean = true

scala> set1
res74: scala.collection.mutable.Set[Int] = Set(1, 2, 3)

3）、map
这里只演示可变map了，都是跟上面一样，操作跟java集合操作类似（需要导入可变集合的包，上面已经导入过）

//创建可变map
scala> val map = new HashMap[String,Int]
map: scala.collection.mutable.HashMap[String,Int] = Map()

//两种方式添加元素，不会生成新的集合
scala> map("zs") = 88

scala> map("ls") = 87

scala> map
res81: scala.collection.mutable.HashMap[String,Int] = Map(zs -> 88, ls -> 87)

scala> map.put("ww",99)
res82: Option[Int] = None

scala> map
res83: scala.collection.mutable.HashMap[String,Int] = Map(ww -> 99, zs -> 88, ls -> 87)

//两种方式移除元素，不会生成新的集合


scala> map -= "ww"
res84: map.type = Map(zs -> 88, ls -> 87)

scala> map.remove("zs")
res85: Option[Int] = Some(88)

scala> map
res86: scala.collection.mutable.HashMap[String,Int] = Map(ls -> 87)