Scala Variables & Data Types

Learn about vals, vars, and Scala's type system.

Variable Declaration

Scala has two types of variables:

val - Immutable (cannot be reassigned)
var - Mutable (can be reassigned)

val name = "Alice"  // Immutable
var age = 25       // Mutable

name = "Bob"       // Error: reassignment to val
age = 26           // OK

Type Inference

Scala has strong type inference. You don't always need to specify types explicitly:

val greeting = "Hello"  // Type inferred as String
val count = 5         // Type inferred as Int
val pi = 3.14159      // Type inferred as Double

You can explicitly declare types if needed:

val greeting: String = "Hello"
val count: Int = 5
val pi: Double = 3.14159

Basic Data Types

Scala has the same basic types as Java but treats them as objects:

Type	Description	Example
Byte	8-bit signed integer	val b: Byte = 127
Short	16-bit signed integer	val s: Short = 32767
Int	32-bit signed integer	val i = 2147483647
Long	64-bit signed integer	val l = 9223372036854775807L
Float	32-bit floating point	val f = 3.14159f
Double	64-bit floating point	val d = 3.14159
Char	16-bit Unicode character	val c = 'A'
Boolean	true or false	val flag = true
String	Sequence of characters	val str = "Hello"

Type Hierarchy

Scala has a unified type hierarchy where all types inherit from Any:

Any
├── AnyVal (value types: Int, Double, Boolean, etc.)
└── AnyRef (reference types: all classes, String, List, etc.)
    └── Null (subtype of all AnyRef types)
└── Nothing (subtype of all types)

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