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Scala - Arrays


Array, which stores a fixed-size sequential collection of elements of the same type.An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Declaring Array Variables

To use an array in a program, you must declare a variable to reference the array and you must specify the type of array the variable can reference.
var z:Array[String] = new Array[String](3)

or

var z = new Array[String](3)
Command z(0) = "Ava"; z(1) = "Nikki"; z(4/2) = "Lisa" There is one more way of defining an array −
var z = Array("Ava", "Nikki", "Lisa")

Processing Arrays

contol structures because all of the elements in an array are of the same type and the size of the array is known.
object Demo {
   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);
   }
}
Output
1.9
2.9
3.4
3.5
Total is 11.7
Max is 3.5

Multi-Dimensional Arrays

This is an array that has three elements each being an array of integers that has three elements.
import Array._

object Demo {
   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();
      }
   }
}
Output
0 1 2
0 1 2
0 1 2

Concatenate Arrays


import Array._

object Demo {
   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 )
      }
   }
}

output

1.9
2.9
3.4
3.5
8.9
7.9
0.4
1.5
Here,

Scala Array Methods


Sr.No Methods with Description
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.