Scala学习(一)

来源：cnblogs　　作者：等木鱼的猫　　时间：2019/1/28 9:33:12　　对本文有异议

1.scala面向行的语言,一句是一行的话,末尾的分号可有可无.

2.数据类型: Byte Short Int Long Float Double Char String Boolean,Unit,Nothing,Any,AnyRef

3.变量声明:(声明时必须赋初始值)
   ①变量: var str : String ="Peanut"
           var str ="Peanut" (不指明数据类型也可以,会被推断为String)

   ②常量: val num: Int =1
           val num = 1 (不指明数据类型,被推断为Int)
           val a,b =10 (a,b都声明为10)

4.集合(collection):

 1 // 定义整型 List
 2 val x = List(1,2,3,4)
 3 
 4 // 定义 Set
 5 val x = Set(1,3,5,7)
 6 
 7 // 定义 Map
 8 val x = Map("one" -> 1, "two" -> 2, "three" -> 3)
 9 
10 // 创建两个不同类型元素的元组
11 val x = (10, "Runoob")
12 
13 // 定义 Option
14 val x:Option[Int] = Some(5)

5.数组Array:

 1 val arr1=Array(1,2,3)   //val arr1=Array[Int](1,2,3)
 2     val arr2=Array("a","b","c") //val arr2=Array[String]("a","b","c")   
 3     val arr3=ArrayBuffer(1,2,3) //val arr3=ArrayBuffer[Int](1,2,3)
 4     arr3+=4  //ArrayBuffer长度可变,使用+=直接在末尾添加
 5     val arr4=ArrayBuffer[String]("a","b","c")  //val arr4=ArrayBuffer[String]("a","b","c")
 6     arr4+=("d","f") 
 7     val arr5=arr1.toBuffer  //Array转ArrayBuffer
 8     val arr6=arr3.toArray   //ArrayBuffer转Array
 9     
10     for(ele<-arr1){ print(ele+",")}//一维数组打印
11     
12     val matrix=ofDim[String](2,3)//二维数组,第一个参数表示外层数组长度,第二个参数表示元素的数组长度
13     matrix(0)=Array("a1","b1","c1")
14     matrix(1)(0)="a2"
15     matrix(1)(1)="b2"
16     matrix(1)(2)="c2"
17     for(i<- 0 until(mytrix.length)){//二维数组打印
18         for(j<- 0 until(mytrix(i).length)){
19             print(mytrix(i)(j)+",")
20         }
21         println()
22     }

6.链表List:

 1  //列表拼接
 2     List("a","b"):::List("c","d") //List(a,b,c,d)
 3     List("a","b")++List("c","d")    //List(a,b,c,d)
 4     List("a","b")++:List("c","d")   //List(a,b,c,d)
 5     List("a","b")::List("c","d")    //List(List(a, b), c, d)
 6     List("a","b"):+List("c","d")    //List(a, b, List(c, d))
 7     //列表长度  length
 8     List("a","b").length //2
 9     //****************************
10     val fList=List("apple","banana","orange")
11     //最后一个元素
12     fList.last  //orange
13     //除最后一个元素外所有元素
14     fList.init  //List("apple","banana")
15     //反转
16     fList.reverse   //List("orange","banana","apple")
17     //取前n个元素
18     fList.take(2)   //List("orange","banana")
19     //取第n个元素(从0开始)
20     fList.apply(2)  //orange
21     fList(2)
22     //修改第n个元素
23     fList.updated(2,"orange2")   //List("apple","banana","orange2")
24     //从第n分成两个表
25     fList.splitAt(1)    //(List("apple"),List("banana","orage"))
26     //除去前n个元素
27     fList.drop(2)   //List("orange")
28     //***************************************
29     val test = List('a','b','c','d','e')
30     //元素的索引
31     test.indices    //Range(0, 1, 2, 3, 4)
32     //索引和元素组成的元组
33     test.indices zip test   //Vector((0,a), (1,b), (2,c), (3,d), (4,e))
34     //元素和索引组成的List
35     test.zipWithIndex   //List((a,0), (b,1), (c,2), (d,3), (e,4))
36     //mkString分割
37     test.mkString   //abcde
38     test.mkString("#")  //a#b#c#d#e
39     test.mkString("[","|","]")  //[a|b|c|d|e]
40     //grouped分组
41     test.grouped(2).mkString(",")   // List(a, b),List(c, d),List(e)
42     //************************
43     //遍历
44     data.foreach{x=>print(x+",")}   //a,b,c,d,e,
45     data.map{x=>print(x+",")}   //a,b,c,d,e,

7.映射Map:

 1   //空哈希表,键为字符串,值为整型
 2     var A:Map[Char,Int]=Map()
 3     //Map键值对
 4     val m1=Map("apple" -> 1,"orange" ->2,"strawberry"->5)
 5     val m2=Map("apple" -> 3,"banana" ->4)
 6     //++ Map合并,右边覆盖左边的
 7     val m3=m1++m2 //Map("apple" -> 3,"orange" ->2,"strawberry"->5,"banana" ->4)
 8     val m4=m2++m1 //Map("apple" -> 1,"orange" ->2,"strawberry"->5,"banana" ->4)
 9    
10     m1.keys.foreach{i=>
11         println("key="+i)
12         println("value="+m1(i))
13     }