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数组是一种可变的、可索引的数据集合。在Scala中用Array[T]的形式来表示Java中的数组形式 T[]。
val numbers = Array(1, 2, 3, 4) //声明一个数组对象val first = numbers(0) // 读取第一个元素numbers(3) = 100 // 替换第四个元素为100val biggerNumbers = numbers.map(_ * 2) // 所有元素乘21234
Scala提供了大量的集合操作:
val a = Array(1,2) val b = Array(3,4) val c = a ++ b //c中的内容是(1,2,3,4)1234
val a = List(1,2) val b = scala.collection.mutable.LinkedList(3,4) val c = a ++: b println(c.getClass().getName())// c的类型是:scala.collection.mutable.LinkedList1234
val a = List(1,2) val c = 0 +: a // c中的内容是 (0,1,2)12
val a = List(1,2,3,4) val c = (10 /: a)(_+_) // 1+2+3+4+10 val d = (10 /: a)(_*_) // 1*2*3*4*10 println("c:"+c) // c:20 println("d:"+d) // d:24012345
foldRight的简写
val a = List(1,2,3,4)scala> val c = (a:\10 )(_+_)c: Int = 20123
将数组中的元素逐个添加到b中
val a = List(1,2,3,4) val b = new StringBuilder() val c = a.addString(b) // c中的内容是 1234123
同上,每个元素用sep分隔符分开
val a = List(1,2,3,4) val b = new StringBuilder() val c = a.addString(b,",") println("c: "+c) // c: 1,2,3,41234
def main(args: Array[String]) { val a = List(1,2,3,4) val c = a.par.aggregate(5)(seqno,combine) println("c:"+c) } def seqno(m:Int,n:Int): Int ={ val s = "seq_exp=%d+%d" println(s.format(m,n)) return m+n } def combine(m:Int,n:Int): Int ={ val s = "com_exp=%d+%d" println(s.format(m,n)) return m+n } /** seq_exp=5+3 seq_exp=5+2 seq_exp=5+4 seq_exp=5+1 com_exp=6+7 com_exp=8+9 com_exp=13+17 c:30 */12345678910111213141516171819202122232425
上面过程可以简写为
scala> val c = a.par.aggregate(5)(_+_,_+_)c: Int = 3012
scala> a.apply(0)res10: Int = 1scala> val first = a(0)first: Int = 1 // 读取第一个元素12345
val chars = Array('a','b','c')println("c:"+chars.charAt(0)) //结果 a12
val chars = Array('a','b','c') println(a.apply(2)) val newchars = chars.clone()123
val chars = Array('a','b','c') val newchars = chars.collect(fun) println("newchars:"+newchars.mkString(",")) //我们通过下面的偏函数,把chars数组的小写a转换为大写的A val fun:PartialFunction[Char,Char] = { case 'a' => 'A' case x => x } /**输出结果是 newchars:A,b,c */123456789
val arr = Array(1,'a',"b")//定义一个偏函数,要求当被执行对象为Int类型时,进行乘100的操作//对于上面定义的对象arr来说,只有第一个元素符合要求 val fun:PartialFunction[Any,Int] = { case x:Int => x*100 }//计算 val value = arr.collectFirst(fun) println("value:"+value)//另一种写法val value = arr.collectFirst({ case x:Int => x*100})1234567891011
val arr = Array("a","b","c") val newarr = arr.combinations(2) newarr.foreach((item) => println(item.mkString(","))) /** a,b a,c b,c */12345678
val a = List(1,2,3,4) val b = List(2,3) println(a.containsSlice(b)) //true123
val a = Array('a', 'b', 'c') val b : Array[Char] = new Array(5) a.copyToArray(b) /**b中元素 ['a','b','c',0,0]*/ a.copyToArray(b,1) /**b中元素 [0,'a',0,0,0]*/ a.copyToArray(b,1,2) /**b中元素 [0,'a','b',0,0]*/12345
scala> import scala.collection.mutable._ import scala.collection.mutable._12 val a = Array('a', 'b', 'c') val b:ArrayBuffer[Char] = ArrayBuffer() a.copyToBuffer(b) println(b.mkString(","))1234
val a = Array(1, 2, 3) val b = Array(4, 5,6) println(a.corresponds(b)(_<_)) //true123
val a = Array(1, 2, 3) println(a.count({ x:Int => x > 2})) // count = 112
val a = Array(1, 2, 3,4) val b = Array(4, 5,6,7) val c = a.diff(b) println(c.mkString) //1,2,31234
val a = Array(1, 2, 3,4,4,5,6,6)val c = a.distinctprintln(c.mkString(",")) // 1,2,3,4,5,6123
val a = Array(1, 2, 3,4)val c = a.drop(2)println(c.mkString(",")) // 3,4123
//下面去除大于2的,第一个元素 3 满足,它后面的元素 2 不满足,所以返回 2,3,4val a = Array(3, 2, 3,4)val c = a.dropWhile( { x:Int => x > 2} )println(c.mkString(",")) //如果数组 a 是下面这样,第一个元素就不满足,所以返回整个数组 1, 2, 3,4val a = Array(1, 2, 3,4) 1234567
val a = Array(3, 2, 3,4)val b = Array(3,4)println(a.endsWith(b)) //true123
val a = Array(3, 2, 3,4) println(a.exists( { x:Int => x==3} )) //true println(a.exists( { x:Int => x==30} )) //false123
val a = Array(3, 2, 3,4)val b = a.filter( { x:Int => x> 2} )println(b.mkString(",")) //3,3,4123
val a = Array(1, 2, 3,4)val b = a.find( { x:Int => x>2} )println(b) // Some(3)123
val a = Array(1, 2, 3,4)val b = a.flatMap(x=>1 to x)println(b.mkString(","))/**1,1,2,1,2,3,1,2,3,4从1开始,分别于集合a的每个元素生成一个递增序列,过程如下11,21,2,31,2,3,4*/1234567891011
val dArr = Array(Array(1,2,3),Array(4,5,6))val c = dArr.flattenprintln(c.mkString(",")) //1,2,3,4,5,6123
def seqno(m:Int,n:Int): Int ={ val s = "seq_exp=%d+%d" println(s.format(m,n)) return m+n } def combine(m:Int,n:Int): Int ={ val s = "com_exp=%d+%d" println(s.format(m,n)) return m+n } val a = Array(1, 2, 3,4) val b = a.fold(5)(seqno) /** 运算过程 seq_exp=5+1 seq_exp=6+2 seq_exp=8+3 seq_exp=11+4 */ val c = a.par.aggregate(5)(seqno,combine) /** 运算过程 seq_exp=5+1 seq_exp=5+4 seq_exp=5+3 com_exp=8+9 seq_exp=5+2 com_exp=6+7 com_exp=13+17 */12345678910111213141516171819202122232425262728
看上面的运算过程发现,fold中,seqno是把初始值顺序和每个元素相加,把得到的结果与下一个元素进行运算
而aggregate中,seqno是把初始值与每个元素相加,但结果不参与下一步运算,而是放到另一个序列中,由第二个方法combine进行处理def seqno(m:Int,n:Int): Int ={ val s = "seq_exp=%d+%d" println(s.format(m,n)) return m+n } val a = Array(1, 2, 3,4) val b = a.foldLeft(5)(seqno) /** 运算过程 seq_exp=5+1 seq_exp=6+2 seq_exp=8+3 seq_exp=11+4 */ /** 简写 (5 /: a)(_+_) */12345678910111213141516
def seqno(m:Int,n:Int): Int ={ val s = "seq_exp=%d+%d" println(s.format(m,n)) return m+n } val a = Array(1, 2, 3,4) val b = a.foldRight(5)(seqno) /** 运算过程 seq_exp=4+5 seq_exp=3+9 seq_exp=2+12 seq_exp=1+14 */ /** 简写 (a :\ 5)(_+_) */12345678910111213141516
val a = Array(1, 2, 3,4) val b = a.forall( { x:Int => x>0}) //true val b = a.forall( { x:Int => x>2}) //false123
val a = Array(1, 2, 3,4) a.foreach(x => println(x*10)) /** 10 20 30 40 */12345678
val a = Array(1, 2, 3,4) val b = a.groupBy( x => x match { case x if (x < 3) => "small" case _ => "big" })12345
val a = Array(1, 2, 3,4,5)val b = a.grouped(3).toListb.foreach((x) => println("第"+(b.indexOf(x)+1)+"组:"+x.mkString(",")))/**第1组:1,2,3第2组:4,5*/1234567
val a = Array(1, 2, 3,4,5)println(a.hasDefiniteSize) //true12
val a = Array(1, 2, 3,4,5)println(a.head) //112
val a = Array(1, 2, 3,4,5)println(a.headOption) //Some(1)12
val a = Array(1, 3, 2, 3, 4)println(a.indexOf(3)) // return 112
val a = Array(1, 3, 2, 3, 4)println(a.indexOf(3,2)) // return 312
val a = Array(1, 3, 2, 3, 4) val b = Array(2,3) println(a.indexOfSlice(b)) // return 2123
val a = Array(1, 3, 2, 3, 2, 3, 4) val b = Array(2,3) println(a.indexOfSlice(b,3)) // return 4123
val a = Array(1, 2, 3, 4) println(a.indexWhere( { x:Int => x>3})) // return 312
val a = Array(1, 2, 3, 4, 5, 6) println(a.indexWhere( { x:Int => x>3},4)) // return 412
val a = Array(10, 2, 3, 40, 5) val b = a.indices println(b.mkString(",")) // 0,1,2,3,4123
val a = Array(10, 2, 3, 40, 5) val b = a.init println(b.mkString(",")) // 10, 2, 3, 40123
val a = Array(1, 2, 3, 4, 5) val b = a.inits.toList for(i <- 1 to b.length){ val s = "第%d个值:%s" println(s.format(i,b(i-1).mkString(","))) } /**计算结果 第1个值:1,2,3,4,5 第2个值:1,2,3,4 第3个值:1,2,3 第4个值:1,2 第5个值:1 第6个值 */1234567891011121314
val a = Array(1, 2, 3, 4, 5) val b = Array(3, 4, 6) val c = a.intersect(b) println(c.mkString(",")) //return 3,41234
val a = Array(1, 2, 3, 4, 5) println(a.isDefinedAt(1)) // true println(a.isDefinedAt(10)) // false123
val a = Array(1, 2, 3, 4, 5) val b = a.iterator //此时就可以通过迭代器访问 b12
val a = Array(1, 2, 3, 4, 5) println(a.last) // return 512
val a = Array(1, 4, 2, 3, 4, 5) println(a.lastIndexOf(4)) // return 412
val a = Array(1, 4, 2, 3, 4, 5) println(a.lastIndexOf(4,3)) // return 112
val a = Array(1, 4, 2, 3, 4, 5, 1, 4) val b = Array(1, 4) println(a.lastIndexOfSlice(b)) // return 6123
val a = Array(1, 4, 2, 3, 4, 5, 1, 4) val b = Array(1, 4) println(a.lastIndexOfSlice(b,4)) // return 0123
val a = Array(1, 4, 2, 3, 4, 5, 1, 4) val b = Array(1, 4) println(a.lastIndexWhere( { x:Int => x<2})) // return 6123
val a = Array(1, 4, 2, 3, 4, 5, 1, 4) val b = Array(1, 4) println(a.lastIndexWhere( { x:Int => x<2},2)) // return 0123
val a = Array(1, 2, 3, 4, 5) println(a.lastOption) // return Some(5)12
val a = Array(1, 2, 3, 4, 5) println(a.length) // return 512
x < 0 if this.length < len x == 0 if this.length == len x > 0 if this.length > len123
val a = Array(1, 2, 3, 4, 5) val b = a.map( { x:Int => x*10}) println(b.mkString(",")) // 10,20,30,40,50123
val a = Array(1, 2, 3, 4, 5) println(a.max) // return 512
val a = Array(1, 2, 3, 4, 5) println(a.maxBy( { x:Int => x > 2})) // return 312
val a = Array(1, 2, 3, 4, 5) println(a.mkString) // return 1234512
val a = Array(1, 2, 3, 4, 5) println(a.mkString(",")) // return 1,2,3,4,512
val a = Array(1, 2, 3, 4, 5) println(a.mkString("{",",","}")) // return {1,2,3,4,5}12
val a = Array(1, 2, 3, 4, 5) val b = a.padTo(7,9) //需要一个长度为 7 的新序列,空出的填充 9 println(b.mkString(",")) // return 1,2,3,4,5,9,9123
val a = Array(1, 2, 3, 4, 5) val b = a.par // "ParArray" size = 512
val a = Array(1, 2, 3, 4, 5) val b:(Array[Int],Array[Int]) = a.partition( { x:Int => x % 2 == 0}) println(b._1.mkString(",")) // return 2,4 println(b._2.mkString(",")) // return 1,3,51234
val a = Array(1, 2, 3, 4, 5) val b = Array(3, 4, 6) val c = a.patch(1,b,2) println(c.mkString(",")) // return 1,3,4,6,4,5 /**从 a 的第二个元素开始,取两个元素,即 2和3 ,这两个元素被替换为 b的内容*/12345
val a = Array(1, 2, 3, 4, 5) val b = a.permutations.toList // b 中将有120个结果,知道排列组合公式的,应该不难理解吧 /**如果是combinations*/ val b = a.combinations(5).toList // b 中只有一个,因为不管怎样排列,都是这5个数字组成,所以只能保留第一个123456
val a = Array(1,2,3,4,1,2,3,4) val b = a.prefixLength( { x:Int => x<3}) // b = 212
val a = Array(1,2,3,4,5) val b = a.product // b = 120 (1*2*3*4*5)12
val fun:PartialFunction[Any,Int] = { case 'a' => 'A' case x:Int => x*100 } val a = Array(1,2,3,4,5) val b = a.reduce(seqno) println(b) // 15 /** seq_exp=1+2 seq_exp=3+3 seq_exp=6+4 seq_exp=10+5 */1234567891011121314
val a = Array(1,2,3,4,5) val b = a.reverse println(b.mkString(",")) //5,4,3,2,1123
val a = Array(1,2,3,4,5) val b = a.reverseMap( { x:Int => x*10} ) println(b.mkString(",")) // 50,40,30,20,10123
val a = Array(1,2,3,4,5) val b = Array(1,2,3,4,5) println(a.sameElements(b)) // true val c = Array(1,2,3,5,4) println(a.sameElements(c)) // false123456
val a = Array(1,2,3,4,5) val b = a.scan(5)(seqno) println(b.mkString(",")) // 5,6,8,11,15,20123
val a = Array(1,2,3,1,1,1,1,1,4,5) val b = a.segmentLength( { x:Int => x < 3},3) // 512
val a = Array(1,2,3,4,5) val b = a.slice(1,3) println(b.mkString(",")) // 2,3123
val a = Array(1,2,3,4,5) val b = a.sliding(3).toList for(i<-0 to b.length - 1){ val s = "第%d个:%s" println(s.format(i,b(i).mkString(","))) } /** 第0个:1,2,3 第1个:2,3,4 第2个:3,4,5 */1234567891011
val a = Array(1,2,3,4,5) val b = a.sliding(3,2).toList //第一个从1开始, 第二个从3开始,因为步进是 2 for(i<-0 to b.length - 1){ val s = "第%d个:%s" println(s.format(i,b(i).mkString(","))) } /** 第0个:1,2,3 第1个:3,4,5 */12345678910
val a = Array(3,2,1,4,5)val b = a.sortBy( { x:Int => x})println(b.mkString(",")) // 1,2,3,4,5123
val a = Array(3,2,1,4,5)val b = a.sortWith(_.compareTo(_) > 0) // 大数在前println(b.mkString(",")) // 5,4,3,2,1123
val a = Array(3,2,1,4,5)val b = a.sorted println(b.mkString(",")) // 1,2,3,4,5123
val a = Array(3,2,1,4,5)val b = a.span( { x:Int => x > 2})println(b._1.mkString(",")) // 3println(b._2.mkString(",")) // 2,1,4,51234
val a = Array(3,2,1,4,5)val b = a.splitAt(2)println(b._1.mkString(",")) // 3,2println(b._2.mkString(",")) // 1,4,51234
val a = Array(0,1,2,3,4,5)val b = Array(1,2)println(a.startsWith(b,1)) // true123
val a = Array(1,2,3,4,5)val b = Array(1,2)println(a.startsWith(b)) // true123
val a = Array(0,1,2,3,4,5)println(a.toString()) //[I@3daa57fbval b = a.stringPrefixprintln(b) //[I1234
val chars = Array('a','b','c','d')val b = chars.subSequence(1,3)println(b.toString) // bc123
val a = Array(1,2,3,4,5)val b = a.sum // 1512
val a = Array(1,2,3,4,5)val b = a.tail // 2,3,4,512
val a = Array(1,2,3,4,5)val b = a.take(3) // 1,2,312
val a = Array(1,2,3,4,5)val b = a.takeRight(3) // 3,4,512
val a = Array(1,2,3,4,5)val b = a.takeWhile( { x:Int => x < 3}) // 1,212
val chars = Array(("a","b"),("c","d"),("e","f"))val b = chars.toMapprintln(b) //Map(a -> b, c -> d, e -> f)123
val chars = Array(Array("a","b"),Array("c","d"),Array("e","f"))val b = chars.transposeprintln(b.mkString(","))123
val a = Array(1,2,3,4,5)val b = Array(6,7)val c = a.union(b)println(c.mkString(",")) // 1,2,3,4,5,6,71234
val chars = Array(("a","b"),("c","d"))val b = chars.unzipprintln(b._1.mkString(",")) //a,cprintln(b._2.mkString(",")) //b,d1234
val chars = Array(("a","b","x"),("c","d","y"),("e","f","z"))val b = chars.unzip3println(b._1.mkString(",")) //a,c,eprintln(b._2.mkString(",")) //b,d,fprintln(b._3.mkString(",")) //x,y,z12345
val a = Array(1,2,3,4,5)a.update(1,9)println(a.mkString(",")) //1,9,3,4,5123
val a = Array(1,2,3,4,5)val b = a.updated(1,9)println(b.mkString(",")) //1,9,3,4,5123
val a = Array(1,2,3,4,5)val b = a.view(1,3)println(b.mkString(",")) //2,3123
val a = Array(1,2,3,4,5)val b = a.withFilter( { x:Int => x>3}).map(x=>x)println(b.mkString(",")) //4,5123
val a = Array(1,2,3,4,5)val b = Array(5,4,3,2,1)val c = a.zip(b)println(c.mkString(",")) //(1,5),(2,4),(3,3),(4,2),(5,1)1234
val a = Array(1,2,3,4,5,6,7)val b = Array(5,4,3,2,1)val c = a.zipAll(b,9,8) //(1,5),(2,4),(3,3),(4,2),(5,1),(6,8),(7,8) val a = Array(1,2,3,4)val b = Array(5,4,3,2,1)val c = a.zipAll(b,9,8) //(1,5),(2,4),(3,3),(4,2),(9,1)1234567
val a = Array(10,20,30,40)val b = a.zipWithIndexprintln(b.mkString(",")) //(10,0),(20,1),(30,2),(40,3)
转自:https://blog.csdn.net/BeiisBei/article/details/103703997