Scala

Introduction

• Scalable Language
• Hybrid functional programming language
• Created by Martin Odersky in 2003
• Compiled to run on Java Virtual Machine
• To improve development productivity, application scalability and overall reliability.
• Scala = Object Oriented Programming + Functional Programming

Tip #1: Before you install Scala check your java version

Open command prompt and type “java –version” and it shows the version of java that has been installed in your computer.

C:\Users\ADMIN>java -version

java version "1.8.0_60"

Java(TM) SE Runtime Environment (build 1.8.0_60-b27)

Java HotSpot(TM) Client VM (build 25.60-b23, mixed mode, sharing)

How to open Scala prompt?

Open command prompt and type command “scala”

If scala is installed in your system, scala version will be displayed as follows.

C:\Users\ADMIN>scala

Welcome to Scala version 2.10.6 (Java HotSpot(TM) Client VM, Java 1.8.0_60).

Type in expressions to have them evaluated.

Type :help for more information.

scala>

How to exit scala prompt?

Type “exit” and press Enter

How to write and run Scala programs?

Step 1: Open notepad and type program

Step 2: Save file with .scala extension

Step 3: Open command prompt and go to the directory in which scala program is saved.

Step 4: Type “scala filename.scala”

Program #1: To display “hello world”

File name: helloworld.scala

Scala code:

println("hello world")

Output:

C:\Users\ADMIN\Desktop>scala helloworld.scala

hello world

Program #2: To find sum of numbers in the list

File name: sum.scala

Scala Code:

var total = 0

val numbers = List(1,2,3,4,5,6)

for (e <- numbers){

total += e

}

println(total)

output:

C:\Users\ADMIN\Desktop>scala sum.scala

21

Program #3: To find addition of two numbers

File name: add.scala

Scala Code:

var a=10

var b=20

println("addition is "+(a+b))

Output:

C:\Users\ADMIN\Desktop\scala programs>scala add.scala

addition is 30

Program #4: Demo on for loop

File name: forloop.scala

Scala Code:

var a=0

for(a <- 1 to 10)

println (a)

Output:

C:\Users\ADMIN\Desktop\scala programs>scala forloop.scala

1

2

3

4

5

6

7

8

9

10

Program #5: Multiplying each number in the list by two using map transformation

File name: mapdemo.scala

Scala Code:

val numbers = List (1,2,3,4,5,6)

println(numbers.map{e => e * 2})

println(numbers.map{e:Int => e * 2}

Output:

C:\Users\ADMIN\Desktop\scala programs>scala mapdemo.scala

List(2, 4, 6, 8, 10, 12)

List(2, 4, 6, 8, 10, 12)

Program #6: Demo on scope of a variable

File name: scope.scala

Scala Code:

val x = 2

def f(y: Int) = y +1 //f is a function that increments y by 1

val result = { //local scope started

val x = f(3); //x is assigned with 4

println(x * x) //prints 4*4=16

} //local scope ended

println(x) //prints 4

Output:

C:\Users\ADMIN\Desktop\scala programs>scala scope.scala

16

2

Program #7: Demo on static typing

File name:statictypingdemo.scala

Scala Code:

var greet = "hello" //no need to mention its data type

println(greet)

greet = "how are you"

println(greet)

Output:

C:\Users\ADMIN\Desktop\scala programs>scala statictypingdemo.scala

hello

how are you

Program #8: Difference between val and var

File name:valvardemo.scala

Scala Code:

var greet1 : String = "hello"

println(greet1)

greet1 = "how are you"

val greet2 : String = "hello"

println(greet2)

greet2 = "how are you" //val can not be changed similar to const

Output:

C:\Users\ADMIN\Desktop\scala programs>scala valvardemo.scala

C:\Users\ADMIN\Desktop\scala programs\valvardemo.scala:7: error: reassignment to val

greet2 = "how are you"

^

one error found

Program #9: Demo on classes

File Name:classdemo.scala

Scala Code:

class Student (val year: Int, var grade: Int) //Student represents class

var s1 = new Student (2016,4) //s1 represents object

println(s1.year)

println(s1.grade)

Output:

C:\Users\ADMIN\Desktop\scala programs>scala classdemo.scala

2016

4

Program #10: Demo on constructors and methods

File name: constructordemo.scala

Scala Code:

class Student (val year: Int, var grade: Int)

{

println("created")

def ChangeGrade (no : Int) //method ChangeGrade

{

println("Changing the grade")

grade = no

println("New Grade is :"+grade) //comma or + can be used

}

}

var s1 = new Student (2005,5) //Constructor can be called

s1.ChangeGrade(25); //all three statements do same thing

s1.ChangeGrade(25)

s1 ChangeGrade 25

Output:

C:\Users\ADMIN\Desktop\scala programs>scala constructordemo.scala

created

Changing the grade

New Grade is :25

Changing the grade

New Grade is :25

Changing the grade

New Grade is :25