- 01Setting up (what you'll need)
- 02Your first output (println)
- 03Variables (val and var)
- 04Type annotations and basic types
- 05Branching (the if expression)
- 06Repeating (the for expression)
- 07Writing your own function
- 08Repeating (the while loop)
- 09Working with lists (List)
- 10Working with maps (Map)
- 11Classes (object orientation)
- 12case class
- 13Inheritance and traits
- 14Pattern matching (the match expression)
- 15The Option type (null safety)
- 16Higher-order functions, map and filter
- 17object (singletons)
- 18Strings and string interpolation
- 19for comprehensions
- 20[Project] Build a small inventory system
Type annotations and basic types
This lesson covers Scala's basic types: Int, Double, Boolean, and String.
Scala's type inference is strong enough that you can usually leave types out, but you can also annotate them explicitly by writing name: Type.
The sample code annotates its variables explicitly, as in val score: Int = 85 and val average: Double = 72.5.
A common early stumble is that every Scala type name starts with a capital letter: Int rather than int, String rather than string. That is because Scala treats even the basic types as objects.
In professional work, spelling types out makes a function's signature and the meaning of its return value clearer to whoever reads it next.
๐งช This site can't compile or run Scala directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).