Difference Between val and var in Scala

1. the val Keyword in Scala
2. the var Keyword in Scala

This tutorial will look at the differences between the val and var keywords for initializing variables in Scala.

the val Keyword in Scala

The val keyword is a constant reference that is immutable, which means the value cannot be changed or modified after initialization. If we still try to change it, we will get an error, as shown below.

Code Snippet:

object MyClass {

    def main(args: Array[String]) {

    val name = "Iron Man"
    name = "Tony Stark"

  }
}

Output:

scala:7: error: reassignment to val
    name = "Tony Stark"

the var Keyword in Scala

The keyword var is a variable that is mutable, meaning we can change or re-assign the values to the variable. The var keyword is useful when a variable changes constantly.

For example, suppose we have a variable account_balance which shows the user’s current account balance. We know that this variable must be updated or changed frequently in a real-world scenario, so we must declare it as var, not val.

Code Snippet:

object MyClass{

def main(args: Array[String]):Unit={

   var account_balance: Int = 1000
   account_balance += 1000 //adding amount
   account_balance -= 50  //withdrawing amount
   account_balance += 200

   println(account_balance)

  }
}

Output:

2150

Let’s look at the differences between val and var keywords in a table.