# Scala Data Types

> A short look at the data types available when using Scala.

- Canonical: https://dennisokeeffe.com/blog/2019-06-18-scala-data-types
- Published: 2019-06-18
- Updated: 2019-06-18

The presumes you have Scala installed on the local system.

This is just the basics on declaring variables in Scala and what data types are available.

## Declaring Variables

Create file `src/main/scala/Playground.scala` with the following.

```scala
object Playground extends App {
  val x: Int = 42
  println(x)
}
```

- `println` will allow us to print to the console.
- Extending `App` allows us to run the file in the command line correctly.
- `val` are immutable - this is the Scala and functional programming way.

Say we remove the explicit type:

```scala
object Playground extends App {
  val x = 42
  println(x)
}
```

This still works as the compiler infers the type to be an `Int`.

## Declaring various types

Below we will run through a declaration of each type.

```scala
object Playground extends App {
  val x: Int = 42
  val y: String = "Hello, Friend!"
  val z: Boolean = true
  val a: Char = 'a' // Note single quotes
  val b: Short = 1234
  val c: Long = 1234123412341234L // Note the L - similar to Java longs
  val d: Float = 2.0f // Note the f - similar to Java
  val e: Double = 2.14 // No marker needed

  /* in order to mutate a variable */
  var f: Int = 1
  f = 2 // this is known as a side effect
}
```

Note that the `val` and `var` keywords have different meanings. `val` is a constant and follows functional, immutable conventions while `var` is mutable and changing a mutable variable is known as a side effect.