Prefer offline? Download PDF of Scala Tutorial Pt. 1.
Scala is both an object-oriented and functional programming language. It is based on the Java Virtual Machine (JVM) and supports seamless integration with Java. Visit the Getting Started page to correctly install Scala on your computer, based on the operating system you have.
Once the installation is complete, run the following command in the terminal to confirm whether Scala has been installed correctly or not.
$ scala --version
Scala code runner version 3.3.0 -- Copyright 2002-2023, LAMP/EPFL
We're ready to go further!
Create a new file named hello.scala with the extension
.scala, as it is the file extension used for Scala
programs. We want to print the text hello, world on the
terminal. To do this, let's write the hello, world text within
double quotes, as strings in Scala are enclosed in double quotes. Single
quotes are reserved for characters.
"hello, world"
print() method is used to print something on terminal.
print("hello, world")
In Scala, the execution of a program starts from the
main() method, similar to other programming languages.
However, defining the main() method in Scala is slightly
different. Instead of a conventional main() method, you can
define any method you prefer and annotate it as the entry point
using the @main annotation.
To define a method in Scala, def keyword is used. Let's
define the hello() method and put this
print() statement within this hello() method.
def hello() = print("hello, world")
In Scala, the = sign is used to separate the method
definition from the method body. Everything after the
= sign represents the body of the
hello() method.
Mark this as main using @main annotation.
@main def hello() = print("hello, world")
Here we have the hello, world program in Scala!
In Scala, the execution of the hello.scala program starts
from the hello() method, which is designated as the main
method for Scala.
In Scala, the execution of a program occurs in two steps. In the first
step, we compile the program using the Scala compiler
(scalac). After successful compilation, the Scala compiler
generates the hello.class file (along with a few other
files). In the second step, the created class is interpreted by the
Scala interpreter (scala).
Following is the command for the step one.
$ scalac hello.scala
Following is the command for the step two.
$ scala hello
hello, world
We just wrote and run the hello, world program in Scala!
Instead of using the print() method, you can use the
println() method in Scala to format the output nicely. This
method appends the \n character at the end of the printed
text, creating a new line.
@main def hello() = println("hello, world")
Run the program again with above two commands and confirm the output.
In Scala, whitespace does not affect the code's functionality. The above code can be written in different ways, and the output will remain the same. For example,
@main def hello() =
println("hello, world")
When your method contains more than one statement in its body, it is recommended to format the code in this way to achieve readability.
Run the program again and confirm the output. You should see the same identical hello, world text as the output.
You can rename the hello() method to
main() (or any other name) in Scala, and there won't be any
issues with this change. Scala considers it as the main method.
The only difference is that after compilation, scalac will
generate main.class (along with a few other files) instead
of hello.class.
@main def main() =
println("hello, world")
Following are the commands we need to run in order to see the output after this new change.
$ scalac hello.scala
$ scala main
hello, world