KotlinTraining

A bunch of Kotlin Examples for learning

Well well, fancy seeing you here. You ready to learn what Kotlin is all about?

Here's a basic study guide subject to change:

Lesson 1

• Learn about Kotlin data classes
• What makes these unique compared to Java?
• What can we use when calling Kotlin from Java?

Exercise

• Run the existing unit tests for PersonTest.kt
• Implement your own data class
  • Call toString on your data class and print results
• Implement your own Kotlin Unit test
• Implement your own Java Unit test that calls Kotlin
• Construct your class using Named constructor arguments
• Create a function with Nullable type as a parameter in a test
  • Call a method on this object with a nullable type
  • What did you have to do?
  • Try calling the function with null
  • Try calling with an actual object
  • What happens? (Set break points or print() to see)

Goals

• Understand what Kotlin data classes do automatically for us
• Understand how to call Kotlin data classes from Java (don’t worry, just works)
• Understand named constructor parameters and what that means for Good Ol’ Builder patterns
• Understand what Non-Nullable and Nullable types are

Lesson 2

• Learn additional basic Kotlin control structures and how they differ from Java
• Examples of converting Optionals to type-safe accessors and null coalescing operators
• Examples of converting streams to Kotlin types

Exercises

• Convert IfElseConversion class to Kotlin. Run tests.
• Convert WhenConversion class to Kotlin. Run tests and implement missing methods.
• Convert OptionalConversion class to Kotlin. Run tests and implement missing methods.
• Convert StreamConversion class to Kotlin. Run tests and implement missing methods.

Goals

• Beginning understanding of "when"
• Understand how if/else differs from Java
• Understand how to convert Optionals to nullable types in Kotlin
• Understand how to convert Streams to Kotlin collections and when to use asSequence()

Lesson 3

• Learn about extension functions
• Learn about basic destructuring

Exercises

1. Create a basic extension function for counting odd numbers in a list, countOdd()
2. Create a more challenging extension function for creating a map from a List, toChunkedMap()
3. Print out petMap using destructuring
4. Use destructing on Animal class

• Get all existing unit tests to pass

Goals

• See how easy it is to extend existing Java library classes, even without needing the source code
• Utilize the stream like conversion skills from Lesson 2.
• Exposure to the different for loop and range syntax in Kotlin (seen in Unit test)
• Exposure to using to infix operator for generating Pairs while constructing a Map