[TOC] # 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 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) # 序列list 空的list是Nil **不可变的list** ~~~ scala> val x = List(1, 2, 3, 4, 5, 6) x: List[Int] = List(1, 2, 3, 4, 5, 6) ~~~ **可变List** ~~~ scala> val lb = scala.collection.mutable.ListBuffer(1, 2, 3, 4, 5) lb: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3, 4, 5) ~~~ ~~~ scala> val lst0 = scala.collection.mutable.ListBuffer[Int](1, 2, 3) lst0: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3) ~~~ ~~~ scala> val lst1 = new scala.collection.mutable.ListBuffer[Int] lst1: scala.collection.mutable.ListBuffer[Int] = ListBuffer() ~~~ ~~~ //将lst1中的元素追加到lst0中,注意:没有生成新的集合 scala> lst0 ++= lst1 res4: lst0.type = ListBuffer(1, 2, 3, 4, 5) ~~~ ~~~ //将lst0和lst1合并成一个新的ListBuffer. 注意:生成了一个新的集合 val lst2 = lst0 ++ lst1 //将元素追加到lst0的后面生成一个新的集合 val lst3 = lst0 :+ 5 ~~~ **添加元素** ~~~ scala> lb += 7 res2: lb.type = ListBuffer(1, 2, 3, 4, 5, 7) scala> lb += (8, 9, 10) res3: lb.type = ListBuffer(1, 2, 3, 4, 5, 7, 8, 9, 10) scala> lb ++= List(-1, -2) res4: lb.type = ListBuffer(1, 2, 3, 4, 5, 7, 8, 9, 10, -1, -2) ~~~ ~~~ //将0插入到lst1的前面生成一个新的List scala> val lst1 = List(1, 2, 3) lst1: List[Int] = List(1, 2, 3) scala> val lst2 = 0 :: lst1 lst2: List[Int] = List(0, 1, 2, 3) scala> val lst3 = lst1.::(0) lst3: List[Int] = List(0, 1, 2, 3) scala> val lst4 = 0 +: lst1 lst4: List[Int] = List(0, 1, 2, 3) scala> val lst5 = lst1.+:(0) lst5: List[Int] = List(0, 1, 2, 3) ~~~ ~~~ //将一个元素添加到lst1的后面产生一个新的集合 scala> val lst6 = lst1 :+ 3 lst6: List[Int] = List(1, 2, 3, 3) ~~~ ~~~ //合并两个list scala> val lst0 = List(4, 5, 6) lst0: List[Int] = List(4, 5, 6) //将两个list合并成一个list scala> val lst7 = lst1 ++ lst0 lst7: List[Int] = List(1, 2, 3, 4, 5, 6) //将lst0加到前面 scala> val lst8 = lst0 ++: lst1 lst8: List[Int] = List(4, 5, 6, 1, 2, 3) ~~~ **并集** ~~~ scala> val l1 = List(5, 6, 7, 4) l1: List[Int] = List(5, 6, 7, 4) scala> val l2 = List(1, 2, 3, 4) l2: List[Int] = List(1, 2, 3, 4) scala> l1.union(l2) res0: List[Int] = List(5, 6, 7, 4, 1, 2, 3, 4) ~~~ **交集** ~~~ scala> l1.intersect(l2) res1: List[Int] = List(4) ~~~ **差集** ~~~ scala> l1.diff(l2) res2: List[Int] = List(5, 6, 7) ~~~ 更新 ~~~ scala> val list1=List(1, 10) list1: List[Int] = List(1, 10) //产生新的集合 scala> list1.updated(1, 50) res5: List[Int] = List(1, 50) ~~~ # 集Set ~~~ scala> val set1 = new scala.collection.immutable.HashSet[Int]() set1: scala.collection.immutable.HashSet[Int] = Set() ~~~ ~~~ //生成一个新的set scala> set1 + 4 res0: scala.collection.immutable.HashSet[Int] = Set(4) ~~~ **判断有没有** ~~~ scala> val set1 = Set(1,2,3,4) set1: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 4) scala> set1(5) res9: Boolean = false scala> set1.contains(7) res10: Boolean = false ~~~ # 映射Map ## 定义,取值 在scala中,把哈希表这种数据结构叫做映射 没有顺序 定义定长map和不定长map ~~~ scala> val m = Map("a"->1, "b"->2, "c"->3) m: scala.collection.immutable.Map[String,Int] = Map(a -> 1, b -> 2, c -> 3) scala> import scala.collection.mutable._ import scala.collection.mutable._ scala> val x = Map("a"->1, "b"->2, "c"->3) x: scala.collection.mutable.Map[String,Int] = Map(b -> 2, a -> 1, c -> 3) ~~~ 取值 ~~~ scala> x("a") res2: Int = 1 scala> x("a")=2 ~~~ 取不到就给默认值 ~~~ scala> m.getOrElse("d", -1) res6: Int = -1 ~~~ ## 添加元素 ~~~ scala> val m1 = scala.collection.mutable.Map(("a", 1), ("b", 2), ("c", 30)) m1: scala.collection.mutable.Map[String,Int] = Map(b -> 2, a -> 1, c -> 30) scala> m1 += ("d" -> 1) res0: m1.type = Map(b -> 2, d -> 1, a -> 1, c -> 30) ~~~ ~~~ scala> m1 += (("e"->11), ("f"->232)) res1: m1.type = Map(e -> 11, b -> 2, d -> 1, a -> 1, c -> 30, f -> 232) ~~~ ## 更新元素 ~~~ scala> val map1 = Map("a"->1, "b"->2, "c"->3) map1: scala.collection.immutable.Map[String,Int] = Map(a -> 1, b -> 2, c -> 3) scala> map1.updated("a",111) res7: scala.collection.immutable.Map[String,Int] = Map(a -> 111, b -> 2, c -> 3) ~~~ ## 遍历 ~~~ scala> for (m <- map1) println(m) (a,1) (b,2) (c,3) ~~~ # option option * some * None ~~~ scala> val map1 = Map("a"->1, "b"->2, "c"->3) map1: scala.collection.immutable.Map[String,Int] = Map(a -> 1, b -> 2, c -> 3) scala> map1.get("a") res0: Option[Int] = Some(1) scala> map1.get("a").get res2: Int = 1 scala> map1.get("ee") res4: Option[Int] = None ~~~ # 拉链 ~~~ import scala.collection.mutable object MyPreDef extends App { val zip1 = List("123", "456") val zip2 = List("孙悟空", "猪八戒") # 把2个zip压缩 val zipResultList = zip1 zip zip2 val zipMap = mutable.Map[String, String]() for (e <- zipResultList) { zipMap += e } println(zipMap) } ~~~ 输出 ~~~ Map(456 -> 猪八戒, 123 -> 孙悟空) ~~~