A: an array of related operations
Fixed-length arrays
val array = Array [String] ( "a", "b", "c") // initialize the contents of the array directly
println (array.mkString ( "|") )
val array = new Array [String] (2) // new data of length 2 is performed by updating the assignment method
array.update (0, "0")
array.update (. 1, ". 1")
the println (Array .mkString ( "|"))
Variable length arrays: an array of buffer
scala.collection.mutable.ArrayBuffer Import
Val an ArrayBuffer new new Data = [String] ();
Data = .- ( ". 3") // single element deletion operation
data .- = ( "3", "2") // single element deletion operation
data. + = ( "1" ) // add a single element operation
data. + = ( "2" , "3", "4") // more elements operating
data. ++ = (Array ( "5", "6", "7")) // array operations variable constant array
data. ++ = (data) // array of variable operation of the variable array
data.trimEnd (2) // removes the last five elements
data.remove (2) // remove the second set of bits a second element
data.remove (2,3) // begin removing the second three elements
val array = data.toArray [String] / / into an array
Through the array and the array buffer
val array = Array [String] ( "a", "b", "c", "d") // into an array
for (i <- array) // through each element
println (i)
for (i <- 0 until array.length ) // iterate length
println (array.apply (i))
for (i <- 0 until ( array.length, 2)) // two elements each jump
println (array.apply (i))
= the Array Array Val [String] ( "A", "B", "C", "D", "E", "F", "H")
for (I <- (0 an until be array.length) .reverse ) // reverse, but when prompted prompt IDE less than this method
println (array.apply (i))
Conversion Array
= the Array Array Val [String] ( "A", "B", "C", "D", "E", "F", "H")
Val for arrayb = (I <- (0 an until be array.length ) .reverse) yield array.apply (i) + "a" // array is an array of objects after the object yield, after the object is an array of buffer array buffer objects yield
val array = Array[String]("a","b","c","d","e","f","h")
val arrayB = array.map { x => x+"a" }.filter { x => x.equals("aa") } //链式编程方法
Common method
val array = Array [Int] ( 1,2,3,4) .sum // summation
val array1 = Array [Int] ( 1,2,3,4) .max // maximum
val array2 = Array [Int ] (1,2,3,4)
array2.sortWith ((A, B) => A> B) .mkString ( "|") // Sort
scaladoc
an ArrayBuffer array2 = Val [Int] (2,2,3,4)
array2.append (. 6) // add a new element
array2.appendAll (array2) // Add a new array
array2.count (x => {if ( x = = 6) true else false}) // number that satisfies the calculated value
. array2 + = (7) // add a new element
val max = array2.max // maximum array
println (array2.mkString ( "|") )
val arrayBuffer = array2.padTo (15, 1234 ) // array into an array of fixed-length, not enough is filled by the second argument
println (arrayBuffer.mkString ( "|") )
Multidimensional Arrays
val array = Array.ofDim[String](2, 4) //两行四列
array(1)(3) = "1234";
println(array.mkString("|"))
Interoperability with Java
import scala.collection.JavaConversions._ // want to convert java scala ways to use this
// which contains a large collection of the scala convert java class
II: Mapping and tuples
Structure mapping
val map = Map ( "aa" -> 4, "bb" -> 5, "cc" -> 6) // This method generates a set of fixed-length map
val map1 = scala.collection.mutable.Map [String, int] () // this method generates a map of a set of variable length
. MAP1 + = (( "dd",. 7))
the println (map1.mkString ( "|"))
Gets the value map
val map = Map ( "aa" -> 4, "bb" -> 5, "cc" -> 6) // This method generates a set of fixed-length map
println (map.getOrElse ( "dd", "100" )) // get dd values, and if not return 100
Updates in the map
val map1 = scala.collection.mutable.HashMap("aa"->4,"bb"->5,"cc"->6) //此方法生成一个定长的map集合
map1.+=(("dd"->7)) //不可变map这个方法是返回新的map
println(map1.mkString("|"))
map1.-=("bb") //删除key
println(map1.mkString("|"))
map1.update("aa", 100) //不可变map没有这个方法
println(map1.mkString("|"))
迭代映射
val map1 = scala.collection.mutable.HashMap("aa"->4,"bb"->5,"cc"->6)
for((key,value)<-map1){
println(key +"|" + value)
}
println()
for(key<-map1.keySet){
println(map1.apply(key))
}
println()
for((key,value)<-map1) yield(value,key) //反转map结构,key，value相互转换
已排序映射
//生成不可变的的排序的map，如果必须要可变的话，建议用treemap
val map1 = scala.collection.immutable.SortedMap("mm"->4,"aa"->5,"cc"->6)
for((key,value)<-map1){
println(key +"|" + value)
}
println()
//生成可变的有顺序的map
val map2 = scala.collection.mutable.LinkedHashMap("mm"->4,"aa"->5,"cc"->6)
for((key,value)<-map2){
println(key +"|" + value)
}
与Java互操作
//将一而终类型的变量转换为另一种类型的变量，这就是JavaConversions魅力
//下面的例子就是将Properties转换为Map类型
import scala.collection.JavaConversions.propertiesAsScalaMap
val map:scala.collection.Map[String,String] = System.getProperties
println(map.toString())
//可用的还有
import scala.collection.JavaConversions.mapAsScalaMap
import scala.collection.JavaConversions.mapAsScalaConcurrentMap
元组
//元组每个元素都可以是不同的类型
val tt = ("aa",11,2.0f,5l)
println(tt._1) //可以用_1，_2，_3，_4访问
拉链
val aa = Array(1,2,3,4)
val bb = Array(5,6,7,8)
val cc = aa.zip(bb)//拉链操作
println(cc.mkString("|"))