Scala 学习笔记之集合

Posted 2020-09-24 AK47Sonic

 1 package com.citi.scala
 2 
 3 object CollectionDemo {
 4   def main(args: Array[String]): Unit = {
 5 
 6     /**
 7      * List
 8      */
 9     println("--------------------------List-------------------------")
10     val numbers = List[Int](11, 22, 33, 44, 55)
11     val numbers1 = List(11, 22, 33, 44, 55)
12     val colors = List[String]("red", "green", "blue")
13     println(s"colors has ${colors.size}, $colors")
14     //取第一个
15     println(colors.head)
16     //去掉第一个，取剩下的
17     println(colors.tail)
18     //取第二个
19     println(colors(1))
20     //遍历
21     for (s <- colors) { println(s) }
22     //高阶函数使用
23     colors.foreach { (s: String) => println(s) }
24     colors.foreach { s => println(s) }
25     colors.foreach { println(_) }
26     val elSize = colors.map((s: String) => s.size)
27     println(elSize)
28     println(numbers.reduce((a: Int, b: Int) => a + b))
29     //初始化空List
30     val ls: List[Int] = List[Int]()
31     val lls: List[Int] = Nil
32     println(ls == lls)
33     //遍历
34     var i = numbers
35     while (!i.isEmpty) {
36       println(i.head)
37       i = i.tail
38     }
39 
40     i = numbers
41     while (i != Nil) {
42       println(i.head)
43       i = i.tail
44     }
45     //cons操作符
46     val consNumbers = 3 :: 2 :: 1 :: Nil
47     println(consNumbers)
48 
49     //List的算数运算
50     println(3 :: 2 :: 1 :: Nil)
51     println(List(7, 6, 5) ::: List(4, 3, 2, 1))
52     println(List(4, 3, 2, 1) ++ List(7, 6, 5))
53     println(List(1, 2) == List(2, 1))
54     println(List(2, 1) == List(2, 1))
55     println(List(1, 2, 3, 2, 1).distinct)
56     println(List(1, 2, 3, 2, 1) drop (2))
57     println(List(4, 3, 2, 1) filter { _ >= 3 })
58     println(List(List(1, 2, 3), List(4, 5, 6)).flatten)
59 
60     println((List(1, 2, 3, 4, 5).partition(_ >= 3)))
61     println(List(1, 2, 3, 4, 5) reverse)
62     println(List(2, 3, 5, 7, 10, 11) slice (1, 4))
63     println(List("apple", "ben") sortBy { s => s.size })
64     println(List(2, 3, 5, 7, 10, 11) splitAt (3))
65     println(List(2, 3, 5, 7, 10, 11) take (3))
66     println(List(1, 2, 3) zip List("a", "b"))
67     println(List(1, 2) :+ 3)
68 
69     /**
70      * Set
71      */
72     println("--------------------------Set-------------------------")
73     val numbersets = Set[Int](11, 22, 11, 33, 44, 55)
74     println(s"numbersets has ${numbersets.size}, $numbersets")
75     println(numbersets.reduce((a: Int, b: Int) => a + b))
76     /**
77      * Map
78      */
79     println("--------------------------Map-------------------------")
80     val colorMap = Map[String, Int]("red" -> 1, "green" -> 2, "yellow" -> 3)
81     println(colorMap("red"))
82     for (pair <- colorMap) { println(pair) }
83 
84   }
85 }

 

运行结果：

--------------------------List-------------------------
colors has 3, List(red, green, blue)
red
List(green, blue)
green
red
green
blue
red
green
blue
red
green
blue
red
green
blue
List(3, 5, 4)
165
true
11
22
33
44
55
11
22
33
44
55
List(3, 2, 1)
List(3, 2, 1)
List(7, 6, 5, 4, 3, 2, 1)
List(4, 3, 2, 1, 7, 6, 5)
false
true
List(1, 2, 3)
List(3, 2, 1)
List(4, 3)
List(1, 2, 3, 4, 5, 6)
(List(3, 4, 5),List(1, 2))
List(5, 4, 3, 2, 1)
List(3, 5, 7)
List(ben, apple)
(List(2, 3, 5),List(7, 10, 11))
List(2, 3, 5)
List((1,a), (2,b))
List(1, 2, 3)
--------------------------Set-------------------------
numbersets has 5, Set(33, 22, 44, 11, 55)
165
--------------------------Map-------------------------
1
(red,1)
(green,2)
(yellow,3)