Scala Tutorial - Scala Variables








In Scala, there are three ways you can define variables: val, var,and lazy val.

Scala allows you to decide whether or not a variable is immutable (read-only) when you declare it.

val

An immutable variable is declared with the keyword val.

This means that it is a variable that cannot be changed.

The following code creates a value with the name x and assigned with a literal number 10. 

val x= 10 

object Main {
  def main(args: Array[String]) {
        val x = 10
        println(x*x ) 

  }
}

x is declared as val and is an immutable variable so you cannot reassign a new value to x.





var

Now let us declare a mutable variable.

A mutable variable is declared with keyword var like: 

object Main {
  def main(args: Array[String]) {
    var y = 10 
    y = 11 
    println(y);

  }
}

You can reassign a new value to y as y is mutable, but you cannot reassign the variable to a different type.

Defining a variable of type Double and assigning it an Int value will work because Int numbers can be converted to Double numbers automatically: 

var z =10.5 
println(z);




Lazy val

Lazy val variables are calculated once, the first time the variable is accessed. Only vals can be lazy variables. 

object Main {
  def main(args: Array[String]) {
        val x = 10e20 
        println(x);
  }
}