book

Kotlin Cookbook

Name: Kotlin Cookbook
Author: Ken Kousen
ISBN: 9781492046639

by Ken Kousen

November 2019

Intermediate to advanced

254 pages

4h 55m

English

O'Reilly Media, Inc.

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Foreword
Preface
Who Should Read This BookHow This Book Is OrganizedConventions Used in This BookUsing Code ExamplesO’Reilly Online LearningHow to Contact UsAcknowledgments
1. Installing and Running Kotlin
1.1. Running Kotlin Without a Local Compiler1.2. Installing Kotlin Locally1.3. Compiling and Running Kotlin from the Command Line1.4. Using the Kotlin REPL1.5. Executing a Kotlin Script1.6. Building a Standalone Application Using GraalVM1.7. Adding the Kotlin Plug-in for Gradle (Groovy Syntax)1.8. Adding the Kotlin Plug-in for Gradle (Kotlin Syntax)1.9. Using Gradle to Build Kotlin Projects1.10. Using Maven with Kotlin
2. Basic Kotlin
2.1. Using Nullable Types in Kotlin2.2. Adding Nullability Indicators to Java2.3. Adding Overloaded Methods for Java2.4. Converting Between Types Explicitly2.5. Printing to Different Bases2.6. Raising a Number to a Power2.7. Using Bitwise Shift Operators2.8. Using Bitwise Boolean Operators2.9. Creating Pair Instances with to
3. Object-Oriented Programming in Kotlin
3.1. Understanding the Difference Between const and val3.2. Creating Custom Getters and Setters3.3. Defining Data Classes3.4. The Backing Property Technique3.5. Overloading Operators3.6. Using lateinit for Delayed Initialization3.7. Using Safe Casting, Reference Equality, and Elvis to Override equals3.8. Creating a Singleton3.9. Much Ado About Nothing
4. Functional Programming
4.1. Using fold in Algorithms4.2. Using the reduce Function for Reductions4.3. Applying Tail Recursion
5. Collections
5.1. Working with Arrays5.2. Creating Collections5.3. Creating Read-Only Views from Existing Collections5.4. Building a Map from a Collection5.5. Returning a Default When a Collection Is Empty5.6. Restricting a Value to a Given Range5.7. Processing a Window on a Collection5.8. Destructuring Lists5.9. Sorting by Multiple Properties5.10. Defining Your Own Iterator5.11. Filtering a Collection by Type5.12. Making a Range into a Progression
6. Sequences
6.1. Using Lazy Sequences6.2. Generating Sequences6.3. Managing Infinite Sequences6.4. Yielding from a Sequence
7. Scope Functions
7.1. Initializing Objects After Construction with apply7.2. Using also for Side Effects7.3. Using the let Function and Elvis7.4. Using let with a Temporary Variable
8. Kotlin Delegates
8.1. Implementing Composition by Delegation8.2. Using the lazy Delegate8.3. Ensuring That a Value Is Not Null8.4. Using the observable and vetoable Delegates8.5. Supplying Maps as Delegates8.6. Creating Your Own Delegates

9. Testing
9.1. Setting the Test Class Life Cycle9.2. Using Data Classes for Tests9.3. Using Helper Functions with Default Arguments9.4. Repeating JUnit 5 Tests with Different Data9.5. Using Data Classes for Parameterized Tests
10. Input/Output
10.1. Managing Resources with use10.2. Writing to a File
11. Miscellaneous
11.1. Working with the Kotlin Version11.2. Executing a Lambda Repeatedly11.3. Forcing when to Be Exhaustive11.4. Using the replace Function with Regular Expressions11.5. Converting to Binary String and Back11.6. Making a Class Executable11.7. Measuring Elapsed Time11.8. Starting Threads11.9. Forcing Completion with TODO11.10. Understanding the Random Behavior of Random11.11. Using Special Characters in Function Names11.12. Telling Java About Exceptions
12. The Spring Framework
12.1. Opening Spring-Managed Bean Classes for Extension12.2. Persisting Kotlin Data Classes12.3. Injecting Dependencies
13. Coroutines and Structured Concurrency
13.1. Choosing Coroutine Builders13.2. Replacing async/await with withContext13.3. Working with Dispatchers13.4. Running Coroutines on a Java Thread Pool13.5. Cancelling Coroutines13.6. Debugging Coroutines
Index

Content preview from Kotlin Cookbook

Chapter 1. Installing and Running Kotlin

The recipes in this chapter help you get up and running with the Kotlin compiler, both from the command line and using an integrated development environment (IDE).

1.1 Running Kotlin Without a Local Compiler

Problem

You want to try out Kotlin without a local installation, or run it on a machine that does not support it (for example, a Chromebook).

Solution

Use the Kotlin Playground, an online sandbox for exploring Kotlin.

Discussion

The Kotlin Playground provides an easy way to experiment with Kotlin, explore features you haven’t used, or simply run Kotlin on systems that don’t have an installed compiler. It gives you access to the latest version of the compiler, along with a web-based editor that allows you to add code without installing Kotlin locally.

Figure 1-1 is a snapshot of the browser page.

Just type in your own code and click the Play button to execute it. The Settings button (the gear icon) allows you to change Kotlin versions, decide which platform to run on (JVM, JS, Canvas, or JUnit), or add program arguments.

Note

As of Kotlin 1.3, the Kotlin function main can be defined without parameters.

The Examples section contains an extensive set of sample programs, organized by topic, that can be executed using an embedded block in a browser. Figure 1-2 shows the “Hello world” program ...

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