Scala: Array in Scala

Array

Scala provides a data structure, the 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.

ArrayBuffer

ArrayBuffer is a mutable data structure which allows you to access and modify elements at specific index. Need to import below object when using ArrayBuffer. All methods are same as Array.

import scala.collection.mutable.ArrayBuffer

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. Here is the syntax for declaring an array variable:

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

var z = new Array[String](3)

You can assign values to individual elements or get access to individual elements; it can be done by using commands like the following:

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

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

MultiDimensional Arrays

There are two main solutions:

1. Use Array.ofDim to create a multidimensional array. You can use this approach to create arrays of up to five dimensions. With this approach you need to know the number of rows and columns at creation time.

Eg: var myMatrix = Array.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 :

myMatrix: Array[Array[Int]] = Array(Array(0, 1, 2), Array(0, 1, 2), Array(0, 1, 2))

2. Create arrays of arrays as needed.

var myMatrix: Array[Array[Int]] = Array(Array(0, 0, 0), Array(0, 0, 0), Array(0, 0, 0))

Processing Arrays:

When processing array elements, we often use either for loop because all of the elements in an array are of the same type and the size of the array is known. Here is a complete example of showing how to create, initialize and process arrays:

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);

}

Output :

1.9

2.9

3.4

3.5

Total is 11.7

Max is 3.5

Methods performed on Array :

val test:Array[Int] = Array(10,20,30,98,9,8)

test.map{x=>println(x)}

//display

println(test.sum) // addition

Output: 175

println(test.max) // maximum number

Output: 98

println(test.min) // minimum number

Output: 8

println(test.product)// product

Output: 42336000

var testFilter:Array[Int] = Array(2,5,3,9,4)

var ans = testFilter.filter(x => (x % 2 == 0) && (x > 3)) // Array(4)

Output: Array(4)

var result = testFilter.exists(_==50) // if present then it will give 'true' if not it will give false

println(result) //false

var testc:Array[Int] = Array(2,2,4,5,6,6,9)

testc.distinct.map{x=>println(x)} // it will give the unique value (2, 4, 5, 6, 9)

val test = Array(10, 20, 30, 40, 10,98,9,8)

var testTake = test.take(4)

testTake.map{x=>println(x)} //it will give (10,20,30,40)

test.takeRight(3) // it will give(98,9,8)

var res_concat = testFilter ++ testc // Array(2,5,3,9,4,2,2,4,5,6,6,9)

var testFilter:Array[Int] = Array(2,5,3,9,4)

var testTake=testFilter.splitAt(2)

Output:

testFilter: Array[Int] = Array(2, 5, 3, 9, 4)

testTake: (Array[Int], Array[Int]) = (Array(2, 5),Array(3, 9, 4))

val test = Array(10, 20, 30, 40, 10,98,9,8)

var testTake=test.partition(_>30)

Output:

testTake: (Array[Int], Array[Int]) =(Array(40, 98),Array(10, 20, 30, 10, 9, 8))