Scala数组使用

1  数组的声明

使用数组时，必须声明一个变量来引用数组，同时确定数组变量的类型，如以下语法：

var z:Array[String] = new Array[String](3)
or
var z = new Array[String](3)

用如下方式赋值：

z(0) = "Zara"; z(1) = "Nuha"; z(4/2) = "Ayan"

或者定义并初始化：

var z = Array("Zara", "Nuha", "Ayan")

2  使用数组

object Test {
   def main(args: Array[String]) {
      var myList = Array(1.9, 2.9, 3.4, 3.5)
      
      // Print all the array elements
      for ( x <- myList ) {
         println( x )
      }

      // Summing all elements
      var total = 0.0;
      for ( i <- 0 to (myList.length - 1)) {
         total += myList(i);
      }
      println("Total is " + total);

      // Finding the largest element
      var max = myList(0);
      for ( i <- 1 to (myList.length - 1) ) {
         if (myList(i) > max) max = myList(i);
      }
      println("Max is " + max);
    
   }
}

结果如下：

C:/>scalac Test.scala
C:/>scala Test
1.9
2.9
3.4
3.5
Total is 11.7
Max is 3.5

3  多维数组

多维数组定义如下：

import Array._
object Test {
   def main(args: Array[String]) {
      var myMatrix = ofDim[Int](3,3)    
      // build a matrix
      for (i <- 0 to 2) {
         for ( j <- 0 to 2) {
            myMatrix(i)(j) = j;
         }
      }
      // Print two dimensional array
      for (i <- 0 to 2) {
         for ( j <- 0 to 2) {
            print(" " + myMatrix(i)(j));
         }
         println();
      }    
   }
}

结果如下：

C:/>scalac Test.scala
C:/>scala Test
0 1 2
0 1 2
0 1 2

4  合并多个数组
使用contact()方法，合并为一个大数组

import Array._

object Test {
   def main(args: Array[String]) {
      var myList1 = Array(1.9, 2.9, 3.4, 3.5)
      var myList2 = Array(8.9, 7.9, 0.4, 1.5)
      var myList3 =  concat( myList1, myList2)
      // Print all the array elements
      for ( x <- myList3 ) {
         println( x )
      }
   }
}

结果如下：

C:/>scalac Test.scala
C:/>scala Test
1.9
2.9
3.4
3.5
8.9
7.9
0.4
1.5

5  用Range创建数组

import Array._
object Test {
   def main(args: Array[String]) {
      var myList1 = range(10, 20, 2)
      var myList2 = range(10,20)
      // Print all the array elements
      for ( x <- myList1 ) {
         print( " " + x )
      }
      println()
      for ( x <- myList2 ) {
         print( " " + x )
      }
   }
}

结果如下：

C:/>scalac Test.scala
C:/>scala Test
10 12 14 16 18
10 11 12 13 14 15 16 17 18 19

6  Scala数组的方法


1  def apply( x: T, xs: T* ): Array[T]

Creates an array of T objects, where T can be Unit, Double, Float, Long, Int, Char, Short, Byte, Boolean.

2  def concat[T]( xss: Array[T]* ): Array[T]

Concatenates all arrays into a single array.

3  def copy( src: AnyRef, srcPos: Int, dest: AnyRef, destPos: Int, length: Int ): Unit

Copy one array to another. Equivalent to Java's System.arraycopy(src, srcPos, dest, destPos, length).

4  def empty[T]: Array[T]

Returns an array of length 0

5  def iterate[T]( start: T, len: Int )( f: (T) => T ): Array[T]

Returns an array containing repeated applications of a function to a start value.

6  def fill[T]( n: Int )(elem: => T): Array[T]

Returns an array that contains the results of some element computation a number of times.

7  def fill[T]( n1: Int, n2: Int )( elem: => T ): Array[Array[T]]

Returns a two-dimensional array that contains the results of some element computation a number of times.

8  def iterate[T]( start: T, len: Int)( f: (T) => T ): Array[T]

Returns an array containing repeated applications of a function to a start value.

9  def ofDim[T]( n1: Int ): Array[T]

Creates array with given dimensions.

10  def ofDim[T]( n1: Int, n2: Int ): Array[Array[T]]

Creates a 2-dimensional array

11  def ofDim[T]( n1: Int, n2: Int, n3: Int ): Array[Array[Array[T]]]

Creates a 3-dimensional array

12  def range( start: Int, end: Int, step: Int ): Array[Int]

Returns an array containing equally spaced values in some integer interval.

13  def range( start: Int, end: Int ): Array[Int]

Returns an array containing a sequence of increasing integers in a range.

14  def tabulate[T]( n: Int )(f: (Int)=> T): Array[T]

Returns an array containing values of a given function over a range of integer values starting from 0.

15  def tabulate[T]( n1: Int, n2: Int )( f: (Int, Int ) => T): Array[Array[T]]

Returns a two-dimensional array containing values of a given function over ranges of integer values starting from 0.