4.5 Scala_Collections

素颜马尾好姑娘i 2022-11-26 07:54 93阅读 0赞

### 文章目录 ###

*  1 Overview
 *   *   *  immutable Array
 *  2 Source
 *   *  2.1 Array
     *   *  immutable
         *  mutable ArrayBuffer
     *  2.2 Set
     *  2.3 Tuple
     *  2.4 List
     *  递归

# 1 Overview #

Scala collections systematically distinguish between mutable and immutable collections  
[Scala官网介绍][Scala]

**scala.collection**  
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### immutable Array ###

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**mutable.**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zOTM4MTgzMw_size_16_color_FFFFFF_t_70 2]  
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# 2 Source #

## 2.1 Array ##

### immutable ###

内容可以变 长度不能改  
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for(elc <- c){
        
        println(elc)
      }

### mutable ArrayBuffer ###

ArrayBuffer 常规操作

scala> var f = ArrayBuffer(1,2)
    f: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2)
    
    scala> f += (3,4,5)
    res11: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5)
    
    scala> f.insert(0,0)
    
    scala> f
    res15: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(0, 1, 2, 3, 4, 5)
    
    scala> f ++= Array(7,8,9)
    res16: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(0, 1, 2, 3, 4, 5, 7, 8, 9)
    
    scala> f.remove(1)
    res17: Int = 1
    
    scala> f
    res18: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(0, 2, 3, 4, 5, 7, 8, 9)
    
    scala> f.remove(0,3)
    
    scala> f
    res20: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(4, 5, 7, 8, 9)

**++=：**

scala> val b1 = ArrayBuffer(1,2,3)
    b1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3)
    
    scala> val b2 = ArrayBuffer(4,5)
    b2: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(4, 5)
    
    scala> b1 ++= b2
    res21: b1.type = ArrayBuffer(1, 2, 3, 4, 5)
    
    scala> b1
    res22: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5)
    
    scala> b2
    res23: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(4, 5)
    
    scala> b1 ++=: b2
    res24: b2.type = ArrayBuffer(1, 2, 3, 4, 5, 4, 5)
    
    scala> b1
    res25: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5)
    
    scala> b2
    res26: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 4, 5)

## 2.2 Set ##

同样分为可变和不可变  
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## 2.3 Tuple ##

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![在这里插入图片描述][20200811173027490.png]  
**负责Tuple**  
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/**
         * res7: ((Int, String), String) = ((4,four),sdfas)
         *
         * tuple._1   ===>   (Int, String)
         * tuple._1._1   ===>   Int
         * */

val (max, min, avg) = method(array)
            println(max + "," + min + "," + avg)
    
            val a = Map("ifeng"->30, "asdf"->31)
    
        //    println(a.get("ifeng").get)
    
            println(a.get("ifeng1").getOrElse(0))
            a.get("spark.executer.nums").getOrElse(2)
    
            for((k,v) <- a) {
        
        //      println(k + "-->" + v)
            }
    
            for(ele <- a.keySet) {
        
        //      println(ele)
            }
    
            a.foreach(println)

val b = scala.collection.mutable.Map("ifeng"->30, "asdf"->31)
            val c = scala.collection.mutable.HashMap[String,Int]()
            println(b.getOrElse("ifeng", 0))
    
            b("asdf")=18
            b.update("asdf",17)
    
            b += ("xingxing" -> 27)
            b.put("J总",28)
    
            b -= "J总"
            b -= ("xingxing","asdf")
    
            val d = scala.collection.immutable.SortedMap("asdf"->31, "ifeng"->30)
    
            val q1 = new mutable.Queue[Int]()
            q1 += 20
            q1.dequeue()
            q1.enqueue(2,6)
    
            q1.head
            q1.tail.tail

## 2.4 List ##

val l = scala.collection.mutable.ListBuffer[Int]()
        l += 2
        l += (3,4,5)
        l ++= List(6,7,8,9)
    l 
        l.toList
        l.toArray
    
        for(ele <- l) {
        
          println(ele)
        }
    
    
        val iterator = l.iterator
        while (iterator.hasNext) {
        
          val i = iterator.next()
          println(i)
        }
    
        l.init
    
        l.drop(1)

## 递归 ##

// 递归方法的定义时，一定要加上返回值类型
        def sum(nums:Int*):Int = {
        
          if(nums.length == 0) {
        
            0 //Int
          } else {
        
            nums.head + sum(nums.tail:_*) //Long
          }
        }
    
        println(sum(1, 2, 3, 4, 5))
    
        val l1 = List(1,2,3,4,5,6,7)
        val l2 = List(4,5,6,7,8,9,10)
    
        l1.union(l2)
        l1.intersect(l2)
        l1.diff(l2)
    
        val l3 = List(30,50,70,60,10,20)
        val iterator1 = l3.sliding(2, 3)
        for(ele <- iterator1) {
        
          println(ele)
        }
      }
    }

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[Scala]: https://docs.scala-lang.org/overviews/collections-2.13/overview.html
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