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Scala val Keyword
In this tutorial, we will learn about the val keyword with example in Scala.
By Shivang Yadav Last updated : April 02, 2023
The 'val' Keyword
Scala's val keyword is used to define a constant or controlled variable in the program. You can skip the declaration of data type in Scala while using val keyword. The variables declared using val keyword are immutable variables.
Immutable Variables are those variables whose value can not be changed in the program. These variable have a fixed value that remains constant throughout the program. Any attempt to change the value causes an error. Example of immutable variables, names, id, etc that are fixed. Usually, we tend to fix strings immutable so that important contained cannot be changed.
Syntax to declare immutable variables using val keyword
val I = 102;
val H : string = "IncludeHelp";
Syntax Explanation
The val keyword is used to initialize the variables. The first initialization is of an int data type which is not declared explicitly, the compiler will take it based on its value. In the second initialization, the data type is explicitly given. This means that irrespective of the value the data type will be a string.
val keyword can define constant variables of all data type. You can not change the value of this variable. Once the value is initialized it is the final value.
Scala example of the val keyword
object MyClass {
def main(args: Array[String]): Unit = {
// Variable Initialized with value52
val myVar = 52;
val name: String = "IncludeHelp"
print("Value of my myVar = " + myVar + "\n")
print("Hello this is " + name)
}
}
Output
Value of my myVar = 52
Hello this is IncludeHelp
Example Explanation
The val keyword here initializes two variables. myVar with value 52 which will itself be initialized as an integer. Another one is name defined as a string.
What if you change the value of val variable. In this code, we have changed the value of myVar.
Example 2
object MyClass {
def main(args: Array[String]): Unit = {
// Variable Initialized with value52
val myVar = 52;
val name: String = "IncludeHelp"
print("Value of my myVar = " + myVar + "\n")
print("Hello this is " + name)
myVar = 23;
print("Value of my myVar = " + myVar + "\n")
}
}
Output
ValKeyword.scala:12: error: reassignment to val
myVar = 23;
^
one error found
cat: /release: No such file or directory
Example Explanation
Changing the value of val variable is an error. The compiler outputs an error "reassignment of val" if you by mistake change its value.