Scala集合概述

时间  2021-01-10

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 "
 
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