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This article is to share with you about the commonly used List list operations in Scala, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Create a list

Scala > val days = List ("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday")

Days: List [String] = List (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday)

Create an empty list

Scala > val l = Nil

L: scala.collection.immutable.Nil.type = List ()

Scala > val l = List ()

L: List [Nothing] = List ()

Create a list with a string

Scala > val l = "Hello":: "Hi":: "Hah":: "WOW":: "WOOW":: Nil

L: List [String] = List (Hello, Hi, Hah, WOW, WOOW)

Create a new list with ":" overlay

Scala > val wow = l: List ("WOOOW", "WOOOOW")

Wow: List [String] = List (Hello, Hi, Hah, WOW, WOOW, WOOOW, WOOOOW)

Get list values through index

Scala > l (3)

Res0: String = WOW

Gets the number of elements with a value length of 3

Scala > l.count (s = > s.length = = 3)

Res1: Int = 2

Returns a new list of the first two elements of l

Scala > l.drop (2)

Res2: List [String] = List (Hah, WOW, WOOW)

Scala > l

Res3: List [String] = List (Hello, Hi, Hah, WOW, WOOW)

Returns a new list of the two elements after l is removed

Scala > l.dropRight (2)

Res5: List [String] = List (Hello, Hi, Hah)

Scala > l

Res6: List [String] = List (Hello, Hi, Hah, WOW, WOOW)

Determine whether l has an element.

Scala > l.exists (s = > s = = "Hah")

Res7: Boolean = true

Filter out elements of length 3

Scala > l.filter (s = > s.length = = 3)

Res8: List [String] = List (Hah, WOW)

Determine whether all elements start with "H"

Scala > l.forall (s = > s.startsWith ("H"))

Res10: Boolean = false

Determine whether all elements end in "H"

Scala > l.forall (s = > s.endsWith ("W"))

Res11: Boolean = false

Print each element

Scala > l.foreach (s = > print (s +'))

Hello Hi Hah WOW WOOW

Take out the first element

Scala > l.head

Res17: String = Hello

Take out the last element

Scala > l.last

Res20: String = WOOW

Remove the last element and generate a new list

Scala > l.init

Res18: List [String] = List (Hello, Hi, Hah, WOW)

Remove the first element and generate a new list

Scala > l.tail

Res49: List [String] = List (Hi, Hah, WOW, WOOW)

Determine whether the list is empty

Scala > l.isEmpty

Res19: Boolean = false

Get the list length

Scala > l.length

Res21: Int = 5

Modify each element, then reverse each element to form a new list

Scala > l.map (s = > {val S1 = s + "- 01"; s1.reverse})

Res29: List [String] = List (10-olleH, 10-iH, 10-haH, 10-WOW, 10-WOOW)

Generate a string separated by commas

Scala > l.mkString (",")

Res30: String = Hello, Hi, Hah, WOW, WOOW

Generate a new list in reverse order

Scala > l.reverse

Res41: List [String] = List (WOOW, WOW, Hah, Hi, Hello)

Sort by alphabetical increment

Scala > l.sortWith (_ .compareto (_) < 0)

Res48: List [String] = List (Hah, Hello, Hi, WOOW, WOW)

These are the common List list operations in Scala, and the editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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