Immutable Variables

In the following lesson, you will learn how to declare an immutable variable.

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Immutable is defined as unchangeable and is precisely what an immutable variable is; unchangeable.

Immutable variables are basically like constants; once they are assigned a value, that value can never change.

Declaring an Immutable Variable

To declare an immutable variable, we use the val keyword. Let’s create a variable named message that is assigned a String value.

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val message: String = "Hello World"
println(message)

Oh no! You just realized you sent the wrong message. Let’s try to reassign a value to the variable message.

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val message: String = "Hello World"
message = "Hello Educative"
println(message)

The above code would give you a runtime error error: reassignment to val letting you know that val cannot be reassigned a value.

In Scala, the general rule is to use the val field unless there’s a good reason not to.

Now, let’s move on to mutable variables that can be reassigned values.