Scala 学习笔记之集合(1)

 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 }