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  • Book Overview & Buying Programming Kotlin
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Programming Kotlin

Programming Kotlin

By : Stephen Samuel, Stefan Bocutiu
3.4 (7)
Buy this Book
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Programming Kotlin

Programming Kotlin

3.4 (7)
By: Stephen Samuel, Stefan Bocutiu
Buy this Book

Overview of this book

Quickly learn the fundamentals of the Kotlin language and see it in action on the web. Easy to follow and covering the full set of programming features, this book will get you fluent in Kotlin for Android.
Table of Contents (14 chapters)
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Preface
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Preface
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What this book covers
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What you need for this book
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Who this book is for
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Conventions
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Reader feedback
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Customer support
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1
1. Getting Started with Kotlin
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1. Getting Started with Kotlin
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Using the command line to compile and run Kotlin code
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Kotlin runtime
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The REPL
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Kotlin for scripting
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Kotlin with Gradle
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Kotlin with Maven
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IntelliJ and Kotlin
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Eclipse and Kotlin
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Mixing Kotlin and Java in a project
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Summary
2
2. Kotlin Basics
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2. Kotlin Basics
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Vals and vars
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Type inference
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Basic types
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Comments
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Packages
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Imports
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String templates
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Ranges
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Loops
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Exception handling
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Instantiating classes
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Referential equality and structural equality
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This expression
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Visibility modifiers
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Control flow as expressions
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Null syntax
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When expression
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Type hierarchy
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Summary
3
3. Object-Oriented Programming in Kotlin
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3. Object-Oriented Programming in Kotlin
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Classes
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Interfaces
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Inheritance
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Visibility modifiers
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Abstract classes
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Interface or abstract class
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Polymorphism
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Overriding rules
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Inheritance versus composition
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Class delegation
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Sealed classes
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Summary
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4. Functions in Kotlin
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4. Functions in Kotlin
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Defining functions
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Single expression functions
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Member functions
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Local functions
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Top-level functions
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Named parameters
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Default parameters
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Extension functions
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Operators
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Function literals
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Tail recursive functions
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Varargs
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Standard library functions
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Generic functions
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Pure functions
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Java from Kotlin
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Kotlin from Java
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Summary
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5. Higher Order Functions and Functional Programming
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5. Higher Order Functions and Functional Programming
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Higher order functions
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Closures
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Anonymous functions
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Function references
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Function-literal receivers
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Functions in the JVM
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Function composition
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Inline functions
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Currying and partial application
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Memoization
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Type alias
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Either
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Custom DSLs
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Validation and error accumulation
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Summary
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6. Properties
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6. Properties
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Why use properties?
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Syntax and variations
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Visibility
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Late initialization
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Delegated properties
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Lazy initializations
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Lateinit versus lazy
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Observables
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A non-null property delegate
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Properties or methods?
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Summary
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7. Null Safety, Reflection, and Annotations
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7. Null Safety, Reflection, and Annotations
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Nullable types
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Smart cast
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Safe null access
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Elvis operator
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Safe casting
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Optionals
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Reflection
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Constructors
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Objects and companions
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Useful KClass properties
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Reflective functions and properties
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Annotations
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Standard annotations
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Runtime annotation discovery
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Summary
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8. Generics
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8. Generics
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Parameterised functions
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Parameterized types
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Bounded polymorphism
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Type variance
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Nothing type
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Type projection
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Type erasure
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Type reification
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Recursive type bounds
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Algebraic data types
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Summary
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9. Data Classes
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9. Data Classes
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Automatic creation of getters and setters
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The copy method
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toString out of the box
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hashCode and equals methods generated for you
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Destructed declarations
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Destructing types
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Data class definition rules
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Limitations
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Summary
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10. Collections
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10. Collections
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Class hierarchy
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Arrays
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Lists
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Maps
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Sets
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Read-only views
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Indexed access
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Sequences
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Summary
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11. Testing in Kotlin
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11. Testing in Kotlin
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Getting started
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Choosing a spec
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Matchers
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Inspectors
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Interceptors
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Project config
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Property testing
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Table-driven testing
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Tags, conditions, and config
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Summary
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12. Microservices with Kotlin
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12. Microservices with Kotlin
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Definition
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Drawbacks
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Why microservices?
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Lagom
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Defining services
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Implementing a Lagom service
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Summary
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13. Concurrency
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13. Concurrency
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Threads
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Deadlocks and livelocks
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Executors
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Race conditions
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Summary

Lazy initializations

There are cases when you want to delay the creation of an instance of your object until its first usage. This technique is known as lazy initialization or lazy instantiation. The main purpose of lazy initialization is to boost performance and reduce your memory footprint. If instantiating an instance of your type carries a large computational cost and the program might end up not actually using it, you would want to delay or even avoid wasting CPU cycles. Imagine you are working on software for a health insurer.

For a customer, you will have a list of claims made. To get this list, you will need to go to the database and load the information. This is quite an expensive process and, if the user does not actually care about the information, it would be a waste of CPU cycles and memory. It is only when the user decides to list the claims that you will go and initialize the claims collection.

Of course, you can write your own code to handle initialization, but this work has...

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Programming Kotlin
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