Scala集合概述

一 集合类图

 

 

二 List[T]

1. C:\Users\lenovo>scala
2. Welcome to Scala2.12.1(JavaHotSpot(TM)64-BitServer VM,Java1.8.0_101).
3. Type in expressions for evaluation.Ortry:help.
5. scala> val a =List(1,2,3,4)
6. a:List[Int]=List(1,2,3,4)
8. scala> val b =0:: a
9. b:List[Int]=List(0,1,2,3,4)
11. scala> val c ="x"::"y"::Nil
12. c:List[String]=List(x, y)
14. scala>"z"::Nil
15. res0:List[String]=List(z)
17. scala>"y":: res0
18. res1:List[String]=List(y, z)
20. scala>"z"::res1
21. res2:List[String]=List(z, y, z)
23. scala> val d = a:::c
24. d:List[Any]=List(1,2,3,4, x, y)
26. scala> a.head
27. res3:Int=1
29. scala> d.head
30. res4:Any=1
32. scala> c.head
33. res5:String= x
35. scala> a.tail
36. res6:List[Int]=List(2,3,4)
38. scala> c.tail
39. res7:List[String]=List(y)
41. scala> a.isEmpty
42. res8:Boolean=false
44. scala>Nil.isEmpty
45. res9:Boolean=true
47. scala> def walkthru(l:List[Int]):String={
48. |if(l.isEmpty)""
49. |else l.head.toString +" "+walkthru(l.tail)
50. |}
51. walkthru:(l:List[Int])String
55. scala> walkthru(a)
56. res11:String="1 2 3 4 "