scala集合操作

阿新 • • 發佈：2018-12-25

object try4 { def main(args: Array[String]) { println("=========================常用操作符===================") val left = List(1,2,3) val right = List(4,5,6) //以下操作等價 println(left ++ right) // List(1,2,3,4,5,6) println(left ++: right) // List(1,2,3,4,5,6) println(right.++:(left)) // List(1,2,3,4,5,6)

println(right.:::(left)) // List(1,2,3,4,5,6) //以下操作等價 println(0 +: left) //List(0,1,2,3) println(left.+:(0)) //List(0,1,2,3) //以下操作等價 println(left :+ 4) //List(1,2,3,4) println(left.:+(4)) //List(1,2,3,4) //以下操作等價 println(0 :: left) //List(0,1,2,3) println(left.::(0

)) //List(0,1,2,3) println("====================================================") println("=========================map操作======================") val nums = List(1,2,3) val square = (x: Int) => x*x println(nums.map(num => num*num)) //List(1,4,9) println(nums.map

(math.pow(_,2))) //List(1.0, 4.0, 9.0) println(nums.map(square)) //List(1,4,9) println("====================================================") println("======================flatmap操作====================") val text = List("A,B,C","D,E,F") val textMapped = text.map(_.split(",").toList) // List(List(A, B, C), List(D, E, F)) println(textMapped) val textFlattened = textMapped.flatten // List(A, B, C, D, E, F) println(textFlattened) val textFlatMapped = text.flatMap(_.split(",").toList) // List(A, B, C, D, E, F) println(textFlatMapped) println("====================================================") println("=======================reduce操作=====================") //nums = List(1,2,3) println(nums.reduce((a,b) => a+b)) //6 println(nums.reduce(_+_)) //6 println(nums.sum) //6 val doubles = List(2.0,2.0,3.0) val resultLeftReduce = doubles.reduceLeft(math.pow) // = pow( pow(2.0,2.0) , 3.0) = 64.0 println(resultLeftReduce) val resultRightReduce = doubles.reduceRight(math.pow) // = pow(2.0, pow(2.0,3.0)) = 256.0 println(resultRightReduce) println("====================================================") println("=========================fold操作======================") val nums2 = List(2,3,4) println(nums2.fold(1)(_+_)) // = 1+2+3+4 = 10 val nums3 = List(2.0,3.0) println(nums3.foldLeft(4.0)(math.pow)) // = pow(pow(4.0,2.0),3.0) = 4096 println(nums3.foldRight(1.0)(math.pow)) // = pow(1.0,pow(2.0,3.0)) = 8.0 println("====================================================") println("=========================filter操作====================") val nums4 = List(1,2,3,4) val odd = nums4.filter( _ % 2 != 0) // List(1,3) println(odd) val even = nums4.filterNot( _ % 2 != 0) // List(2,4) println(even) println("====================================================") println("=============diff, union, intersect操作===============") val nums5 = List(1,2,3) val nums6 = List(2,3,4) val diff1 = nums5 diff nums6 // List(1) println(diff1) val diff2 = nums6.diff(nums5) // List(4) println(diff2) val union1 = nums5 union nums6 // List(1,2,3,2,3,4) println(union1) val union2 = nums6 ++ nums5 // List(2,3,4,1,2,3) println(union2) val intersection = nums5 intersect nums6 //List(2,3) println(intersection) println("====================================================") println("==================groupBy, grouped操作================") val data = List(("HomeWay","Male"),("XSDYM","Femail"),("Mr.Wang","Male")) val group1 = data.groupBy(_._2) // Map("Male" -> List(("HomeWay","Male"),("Mr.Wang","Male")),"Female" -> List(("XSDYM","Femail"))) println(group1) val group2 = data.groupBy{case (name,sex) => sex} // Map("Male" -> List(("HomeWay","Male"),("Mr.Wang","Male")),"Female" -> List(("XSDYM","Femail"))) println(group2) val fixSizeGroup = data.grouped(2).toList // List(List((HomeWay,Male), (XSDYM,Femail)), List((Mr.Wang,Male))) println(fixSizeGroup) println("====================================================") println("========================scan操作=====================") val nums7 = List(1,2,3) println(nums7.scan(10)(_+_)) // List(10,10+1,10+1+2,10+1+2+3) = List(10,11,13,16) val nums8 = List(1.0,2.0,3.0) println(nums8.scanLeft(2.0)(math.pow)) // List(2.0,pow(2.0,1.0), pow(pow(2.0,1.0),2.0),pow(pow(pow(2.0,1.0),2.0),3.0) = List(2.0,2.0,4.0,64.0) println(nums8.scanRight(2.0)(math.pow)) // List(2.0,pow(3.0,2.0), pow(2.0,pow(3.0,2.0)), pow(1.0,pow(2.0,pow(3.0,2.0))) = List(1.0,512.0,9.0,2.0) println("====================================================") println("=========================take操作======================") val nums9 = List(1,1,1,1,4,4,4,4) println(nums9.take(4)) // List(1,1,1,1) println(nums9.takeRight(4)) // List(4,4,4,4) println(nums9.takeWhile( _ == nums.head)) // List(1,1,1,1) println("====================================================") println("========================drop操作=====================") val nums10 = List(1,1,1,1,4,4,4,4) println(nums10.drop(4)) // List(4,4,4,4) println(nums10.dropRight(4)) // List(1,1,1,1) println(nums10.dropWhile( _ == nums.head)) // List(4,4,4,4) println("====================================================") println("===============span,splitAt,partition操作=============") val nums11 = List(1,1,1,2,3,2,1) val (prefix,suffix) = nums11.span( _ == 1) // prefix = List(1,1,1), suffix = List(2,3,2,1) println((prefix,suffix)) val (prefix2,suffix2) = nums11.splitAt(3) // prefix = List(1,1,1), suffix = List(2,3,2,1) println((prefix2,suffix2)) val (prefix3,suffix3) = nums11.partition( _ == 1) // prefix = List(1,1,1,1), suffix = List(2,3,2) println((prefix3,suffix3)) println("====================================================") println("========================padTo操作=====================") val nums12 = List(1,1,1) println(nums12.padTo(6,2)) println("====================================================") println("=============combinations&permutations操作============") val nums13 = List(1,1,3) println(nums13.combinations(2).toList) //List(List(1,1),List(1,3)) println(nums13.permutations.toList) // List(List(1,1,3),List(1,3,1),List(3,1,1)) println("====================================================") println("========================zip操作======================") val alphabet = List("A","B","C") val nums14 = List(1,2) val zipped = alphabet zip nums14 // List(("A",1),("B",2)) println(zipped) val zippedAll = alphabet.zipAll(nums14,"*",-1) // List(("A",1),("B",2),("C",-1)) println(zippedAll) val zippedIndex = alphabet.zipWithIndex // List(("A",0),("B",1),("C",3)) println(zippedIndex) val (list1,list2) = zipped.unzip // list1 = List("A","B"), list2 = List(1,2) println((list1,list2)) val (l1,l2,l3) = List((1, "one", '1'),(2, "two", '2'),(3, "three", '3')).unzip3 // l1=List(1,2,3),l2=List("one","two","three"),l3=List('1','2','3') println((l1,l2,l3)) println("====================================================") println("=======================slice操作=====================") val nums15 = List(1,2,3,4,5) println(nums15.slice(2,4)) //List(3,4) println("====================================================") println("======================sliding操作====================") val nums16 = List(1,1,2,2,3,3,4,4) val groupStep1 = nums16.sliding(2,2).toList //List(List(1,1),List(2,2),List(3,3),List(4,4)) println(groupStep1) val groupStep2 = nums16.sliding(2).toList //List(List(1,1),List(1,2),List(2,2),List(2,3),List(3,3),List(3,4),List(4,4)) println(groupStep2) println("====================================================") println("======================updated操作====================") val nums17 = List(1,2,3,3) val fixed = nums17.updated(3,4) // List(1,2,3,4) println(fixed) println("====================================================") } }

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