Posts in the “scala” category

This is a “cheat sheet” for the Scala 3 programming language. I initially wrote it for my book Learn Functional Programming The Fast Way, but I thought I’d share it here as well.

If you want to see many more details about Scala 3, see:

• The free, online Scala 3 Book (which I co-wrote)
• My book, Learn Scala 3 The Fast Way!
• The Scala Cookbook (2nd Edition)
• Functional Programming, Simplified
• My free 115-page e-book, Learning Recursion

If you ever need some good ScalaJ-HTTP examples, see the test files in the project, including this HttpBinTest.scala file. That file currently shows a number of good ScalaJ-HTTP examples, including GET, POST, and redirect examples with Scala.

See that page for a full list of examples, but for my own use, here are a few of them.

Scala FAQ: Can you show an example of the Scala 3 if-then-else-if syntax?

Scala 3 solution

Here’s an example of the Scala 3 if-then/else-if/else syntax, as used as the body of a method:

Scala List class FAQ: How do I create a List in Scala? (Also asked as, how do I create and initially populate a List in Scala?)

You can create a Scala List in several different ways, including these approaches:

If you’d like to get started working with the Scala ZIO functional programming (FP) library, here are two little ZIO 101 and ZIO 102 “Hello, world” examples that you can run with Scala CLI and Scala 3.

This post is sponsored by my new book,
Learn Functional Programming Without Fear.

FP: ZIO + Scala CLI example: “Hello, world” 101

First, here’s a complete ZIO “Hello, world” example that shows everything you need to get started using ZIO with Scala CLI:

I ran into a strange problem this weekend where I noticed a huge difference between the way a Scala Future and a Thread worked for the exact same code. I think I’m pretty aware of the obvious differences between futures and threads, so this really caught me by surprise. If/when I figure out why there was such a difference in behavior for the given problem I’ll post that information here.

A Scala Thread example

While that problem will haunt me for a while, what I really want to post here today is a simple Scala Thread example:

As a brief note today, this is a very little ZIO HTTP Server application. I’m sharing it here because it’s currently a fairly simple example, and also because I show how to include the necessary ZIO dependencies using Scala-CLI:

Scala collections FAQ: How can I convert a Scala array to a String? (Or, more, accurately, how do I convert any Scala sequence to a String.)

A simple way to convert a Scala array to a String is with the mkString method of the Array class. (Although I've written "array", the same technique also works with any Scala sequence, including Array, List, Seq, ArrayBuffer, Vector, and other sequence types.)

Scala FAQ: Can you share some examples of the Scala if/then/else syntax? Also, can you show a function that returns a value from an if/then/else statement?

In its most basic use, the Scala if/then/else syntax is very similar to Java:

As I’ve been learning more about Scala and functional programming, I’ve been looking at accomplishing more tasks with recursive programming techniques. As part of my studies I put together a number of Scala recursion examples below, including:

I’ve known about using Scala’s zipWithIndex method for quite some time. I used it in for loops to replace counters, and it works like this:

scala> List("a", "b", "c").zipWithIndex
res0: List[(String, Int)] = List((a,0), (b,1), (c,2))

I learned about using zip with Stream last night while reading Joshua Suereth’s book, Scala In Depth. It works like this:

Scala FAQ: How do I convert a String to Int in Scala?

Solution: Use 'toInt()'

If you need to convert a String to an Int in Scala, just use the toInt method, which is available on String objects, like this:

A powerful Scala idiom is to use the Option class when returning a value from a function that can be null. Simply stated, instead of returning one object when a function succeeds and null when it fails, your function should instead return an instance of an Option, where the instance is either:

1. In the success case, return an instance of the Scala Some class
2. In the failure case, return an instance of the Scala None class

Because Some and None are both children of Option, your function signature just declares that you're returning an Option that contains some type (such as the Int type shown below). At the very least, this has the tremendous benefit of letting the user of your function know what’s going on.

Scala FAQ: How do I sort a sequential collection in Scala? (Or, how do I implement the Ordered trait in a custom class so I can use the sorted method (or operators like <, <=, >, and >=) to compare instances of my class?

I’ve been slowly working on a series of new Scala programming books, and today I’m proud to announce the first of these:

Starting today you can buy the PDF version of Learn Scala 3 The Fast Way! for just ten dollars — $10 (USD) — at this Gumroad.com URL.

Note: I don't have any immediate solutions in this article; it's more of a discussion of where I'm at today when looking at handling money/currency in Scala.

As a quick note, I've started to look at handling money/currency in Scala, and I'm also starting to explore a couple of money/currency libraries.

I've been trying to find some good Scala currency and money libraries lately, and I just ran across the following list of projects on the Joda Money Github project. That URL contains the following list of Java and JVM-based projects that should all be usable in Scala:

Scala shell script FAQ: How do I create a Unix/Linux shell script to run a small Scala script?

If you want to run a Scala script as a Unix or Linux shell script -- such as hello.sh -- write your script like this:

March 24, 2024: Here’s a summary of my current free online Scala and functional programming training courses:

• Introduction to Scala 3 (video course)
• Introduction to Functional Programming (video course)
• Advanced Scala 3 (video course)

If you’re interested in 100% Free online Scala and FP video training courses, I hope these online video courses are helpful.