Atomic Kotlin Review
12 Feb 2021
This is a reference to a printed edition from January 2021 (627 pages)
From Authors:
Bruce Eckel (Thinking in Java)
Svetlana Isakova (Kotlin in Action)
As a Lean Pub released book the process doesn’t allow for the creating of indices, however it is structured with a summary in the Table of Contents.
The booked is aimed at both novices and experienced programmers as Kotlin cherry-picks from newer languages and supports historical OOP features.
The book breaks these topics down into seven sections ending with Kotlin’s Power Tools.
For developers already experienced with Java and its frameworks/libraries, who are looking to switch to Kotlin, this book may not provide the most direct answers.
Why Kotlin?
Kotlin has had the benefit to pick from a field of tested language features in mainstream use particularly C-Sharp, Scala, Swift, Python, even Visual Basic to address most of the pitfalls of Java elaborated in Effective Java
A couple of the main improvements are addition of null safe types and removal of the Java Generics implementation with a new type system somewhat borrowed from C Sharp (in and out variance) and Scala’s (Any and Nothing) hierarchy
Kotlin intentionally blends styles, and covered in this Book, of imperative mutable data, class object orientated data, functional algebra to manipulate data in lambdas and collections
If you haven’t been a programmer across the century, migrating from one language to another, there are some notes about where languages features and constructs originated in Kotlin
Some areas that Kotlin does well compared to Java are data classes, lambdas, expressions, no-semi colons, easy to add extension methods
Even if Java continues to add features, like records OpenJDK, it will still be very clunky and verbose
Kotlin strives to be it’s own language as well - for example to jettison the ‘Java’ style for syntax - opting for something more like Visual Basic or Python use
On the other-hand, one area where Kotlin is not 100% portable with Java is the lack of a package private scope
This Java default visibility scope may have been dropped as the Kotlin scoping is more suitable for cross platform use (e.g modules). There is still a debate to this day
Advocates of package private argue it allows a logical public interface for the hiding of private implementation classes
The counter argument is that it is only private if you don’t look
Decisions to make classes final - a number of popular frameworks use these Java built in defaults that make adoption of Kotlin that bit difficult
Also, setting defaults different from Java will normally please some, like library authors but annoy new comers that don’t know why they are prevented from doing something
Atomic Kotlin Book covers a basic example of Generics and Co-variance and Contra-variance, for more detailed explanations readers will have to go elsewhere
The importance of Testing is introduced early with the basics but advanced topics like Multithreading and Co-routines are not mentioned in the Book
For readers new to JVM languages, they will need to know about type erasure and Kotlin’s support for some kind of type capture reification at compile time
Overall this Book gives a very readable, well spaced out and thorough walk around Kotlin’s core features that are likely to remain in 1.x versions of Kotlin and there is online exercise content to supplement Atomic Kotlin
On using more advanced features or Android developers who would look to more specific books like Effective Kotlin or resources about Android Basics