Scala array collection of learning (c)

I. Introduction

Second, the definition of an array

　　2.1 Definitions ordinary arrays

　　2.2 the definition of an array variable

Third, the usual method Array

　　3.1 Array general method

　　3.2 Variable Array common method

 

 

 

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I. Introduction

　　A specified array elements are accessed through the index. Once the array defined, you can change its inner elements, a single length of the array can not be changed.

Second, the definition of an array

　　2.1 Definitions ordinary arrays

{ArrDemo Object 
    DEF main (args: the Array [String]): Unit = { 

        // definition of length 5, an integer type array 
        var ARR = new new the Array [Int] (5 ) 

        // defines a length of 5, any type array 
        var of arr1 = new new the array [the Any] (. 5 ) 
        
        // directly defined inside the array of content 
        var arr2 is the array = (. 1, 2,. 3,. 4,. 5 ) 

    } 
}

 

　　2.2 the definition of an array variable

import scala.collection.mutable.ArrayBuffer

object ArrayDemo2 {
    def main(args: Array[String]): Unit = {
        
        var ab = ArrayBuffer[Int]()
        
    }
}

Third, some methods array

　　3.1 Array general method

{ArrDemo Object 
    DEF main (args: the Array [String]): Unit = { 

        var arr2 is = the Array (. 1, 2,. 3,. 4,. 3 ) 

        // Map method / array is an array mapping each element of some kind operation, (x: Int) => x * 2 is an anonymous function, x is each element of the array
         // e.g. 
        var tmp = arr2.map (X => X * 2 ) 
        Print (tmp.toBuffer)   // an ArrayBuffer (2,. 4,. 6,. 8,. 6) 

        
        Val words = the Array ( "Hello Hello Jim Tom Jerry Hello", "Hatano Hello" ) 
        var TMP2 = words.map (X => x.split ( "" )) 
        Print (TMP2 ( 0) .toBuffer, TMP2 (1) .toBuffer) // (ArrayBuffer(hello, tom, hello, jim, hello, jerry),ArrayBuffer(hello, Hatano))

        // 扁平化操作，数组内的数组合并
        var tmp3 = tmp2.flatten
        print(tmp3.toBuffer) // ArrayBuffer(hello, tom, hello, jim, hello, jerry, hello, Hatano)


        // flatMap方法是 map再flatten
        var arr3 = Array("hello tom hello jim hello jerry", "hello Hatano")
        arr3.flatMap(x => x.split(" "))
        print(arr3.toBuffer) // ArrayBuffer(hello tom hello jim hello jerry, hello Hatano)
        

    }
}

　　3.2 Variable array method

Import scala.collection.mutable.ArrayBuffer 

Object ArrayDemo2 { 
    DEF main (args: the Array [String]): Unit = { 

        var ab & = an ArrayBuffer [Int] () 

        // Adds elements 
        ab.append (. 1 ) 
        ab.append ( 2 ) 
        ab.append ( . 1 ) 

        // Appends a single or multiple 
        ab & + =. 4 
        ab & + = (5,5,3,2 ) 

        // append an array 
        ab & ++ the array (. 3,. 4 ) 
        
        // at some position of the insertion element (index value) 
        ab.insert (2,. 3 ) 


        // array remove elements (index position) 
        ab.remove (. 1) 

        // change the array element (the index, the new value) 
        ab.update (0,. 3 ) 

        // Get variable array element 
        Print (ab.toBuffer) 

    } 

}