Kotlin Development

Outline

Introducing Kotlin on the JVM

• Four coding paradigms within Java 9
• Limits imposed by backwards compatability
• The new consenses in language design
• A brief history of the Kotlin language
• Comparing Kotlin to Scala and Clojure
• Comparing Kotlin to Swift and TypeScript

First Steps with Kotlin

• Declarations and type inference
• The Kotlin type system and conversions
• Packages, access levels and default imports
• Nullable types and operators for null safety
• Keywords for selection and iteration
• Options for declaring basic functions
• Overloading, infix functions and ranges

Object Orientation

• Decompiling Kotlin classes using ‘javap’
• Understanding properties and backing fields
• A detailed explanation of primary constructors
• Adding extra fields and secondary constructors
• Extra features automatically added to data classes
• Overriding, abstract classes and interfaces
• Using object expressions as event handlers
• Object declarations and companion objects

Agile Development

• Review of core principles of Agile development
• Refactoring Kotlin code within IntelliJ
• Performing TDD in Kotlin using KotlinTest
• Using Mockito to separate types from dependencies
• Options for BDD and Property Based Testing

Generics and Type Parameters

• Revision of covariance and contravariance
• Common issues with bounded wildcards in Java
• How declaration site variance simplifies generics
• Support for use-site variance (aka type projection)
• Declaring single and multiple constraints on types

Working with Collections Part 1

• Introducing the Kotlin collections library
• Working with mutable and immutable collections
• Support for destructuring types and collections

Functional Programming

• Working with function references and code blocks
• Declaring functions as parameters and return types
• Using higher order functions for internal iteration
• Creating your own versions of ‘filter’, ‘map’ etc…
• Using higher order functions to prevent duplication
• Understanding partial invocation and currying
• Choosing between code blocks and local functions
• Common misunderstandings regarding enclosure

Working with Collections Part 2

• Basic coding using ‘filter’, ‘map’ and ‘forEach’
• Testing against a predicate using ‘all’, ‘any’ etc…
• Why ‘flatMap’ is such as valuable operation in FP
• Distinguishing between ‘fold’, ‘foldRight’ and ‘reduce’
• Converting between collection types within FP

Interoperability Between Kotlin and Java

• General guidelines for mixed language codebases
• Considerations when calling Java libraries from Kotlin
• Obtaining and using java.lang.Class objects in Kotlin
• Tips and idioms for calling Kotlin libraries from Java code

Creating Spring Microservcies in Kotlin

• Revision of the Spring Framework and RESTful architecture
• Creating Spring Boot projects in Kotlin via the Spring Initializr
• Declaring Spring MVC based RESTful services using annotations
• Injecting dependencies and configuring exception handling
• Creating reactive microservices using Spring WebFlux
• Taking advantage of the Kotlin specific routing DSL

Creating Mobile Applications in Kotlin

• Revision of the Android platform and Dalvik VM
• Installing Android Studio and configuring emulators
• Introducing the sample project for tracking expenses
• Reverse engineering the sample activities and layouts
• Performing dependency injection on Android with Dagger 2