Scala Demo Examples

Practice programs, one file each. Every demo is self-contained, commented, and needs nothing but a JDK and scala-cli — see Setup & Toolchain.

How to use: click View to open a file in the code viewer, read its comments, download it, then run it on your machine.

scala-cli run 01_hello.scala    # compile and run a demo
scala-cli test 18_testing.scala # run the MUnit test demo

Foundations

Values, types, strings — the vocabulary of the language.

#	Description	Link
1	Hello, World	View
2	Variables: val vs var	View
3	Scalar Types & Casting	View
4	Strings & Formatting	View

Functions & Control Flow

Named and anonymous functions, branching, loops, and collections.

#	Description	Link
5	Functions & Higher-Order Functions	View
6	if/else and match	View
7	for, while, labeled break	View
8	List, Map, Set & Pipelines	View

Classes, Inheritance & Traits

The object-oriented side of Scala.

#	Description	Link
9	Classes & Constructors	View
10	Inheritance & Override	View
11	Traits	View
12	Case Classes	View
13	Companion Objects	View

Generics & Functional Error Handling

Type parameters, algebraic data types, and Option/Try/Either.

#	Description	Link
14	Option, Try & Either	View
15	Generics	View
16	Sealed Traits & Exhaustive Matching	View

Professional

Futures and tests — the skills a production codebase expects.

#	Description	Link
17	Concurrency with Future	View
18	Unit Tests (MUnit)	View

Study Projects

Small programs that compose several lessons into one working piece.

#	Description	Link
19	Word Frequency Counter	View
20	In-Memory Todo List	View

Practice move: after running each demo, change one thing on purpose — drop a case from a sealed trait match, call .get on a None, remove the implicit ExecutionContext — and read the compiler or runtime error before fixing it.