/Kotlin-RoadMap

Apache License 2.0Apache-2.0

Kotlin-RoadMap v1.0.0-alpha01

Kotlin v1.9.22

1. Types

Numbers

  • Integer types
  • Floating-point types
  • Literal constants for numbers
  • Numbers representation on the JVM
  • Explicit number conversions
  • Operations on numbers
    • Division of integers
    • Bitwise operations
    • Floating-point numbers comparison

Unsigned integer types

  • Unsigned arrays and ranges
  • Unsigned integers literals
  • Use cases
    • Non-goals

Booleans

Characters

Strings

  • String literals
    • Escaped strings
    • Multiline strings
  • String templates
  • String formatting

Arrays

  • When to use arrays
  • Create arrays
    • Nested arrays
  • Access and modify elements
  • Work with arrays
    • Pass variable number of arguments to a function
    • Compare arrays
    • Transform arrays
    • Sum
    • Shuffle
    • Convert arrays to collections
  • Primitive-type arrays

Type checks and casts

  • is and !is operators
  • Smart casts
  • "Unsafe" cast operator
  • "Safe" (nullable) cast operator

2. Control Flow

Conditions and loops

  • If expression
  • When expression
  • For loops
  • While loops
  • Break and continue in loops

Returns and jumps

  • Break and continue labels
  • Return to labels

Exceptions

  • Exception classes
    • Try is an expression
  • Checked exceptions
  • The Nothing type
  • Java interoperability

Packages and imports

  • Default imports
  • Imports
  • Visibility of top-level declarations

3. Functions

Functions

  • Function usage
    • Parameters
    • Default arguments
    • Named arguments
    • Unit-returning functions
    • Single-expression functions
    • Explicit return types
    • Variable number of arguments (varargs)
      • Infix notation
  • Function scope
    • Local functions
    • Member functions
  • Generic functions
  • Tail recursive functions

Lambdas

  • Higher-order functions and lambdas
  • Function types
    • Instantiating a function type
    • Invoking a function type instance
    • Inline functions
  • Lambda expressions and anonymous functions
    • Lambda expression syntax
    • Passing trailing lambdas
    • it: implicit name of a single parameter
    • Returning a value from a lambda expression
    • Underscore for unused variables
    • Destructuring in lambdas
    • Anonymous functions
    • Closures
    • Function literals with receiver

Inline functions

  • noinline
  • Non-local returns
  • Reified type parameters
  • Inline properties
  • Restrictions for public API inline functions

Operator overloading

  • Unary operations
    • Unary prefix operators
    • Increments and decrements
  • Binary operations
    • Arithmetic operators
    • in operator
    • Indexed access operator
    • invoke operator
    • Augmented assignments
    • Equality and inequality operators
    • Comparison operators
    • Property delegation operators
  • Infix calls for named functions

Builders

  • Type-safe builders
  • How it works
  • Scope control: @DslMarker
  • Full definition of the com.example.html package
  • Using builders with builder type inference
  • Writing your own builders
    • Requirements for enabling builder inference
    • Supported features
  • How builder inference works
    • Postponed type variables
    • Contributing to builder inference results

4. Classes

Basics

  • Constructors
    • Secondary constructors
  • Creating instances of classes
  • Class members
  • Inheritance
  • Abstract classes
  • Companion object

Inheritance

  • Overriding methods
  • Overriding properties
  • Derived class initialization order
  • Calling the superclass implementation
  • Overriding rules

Properties

  • Declaring properties
  • Getters and setters
    • Backing fields
    • Backing properties
  • Compile-time constants
  • Late-initialized properties and variables
    • Checking whether a lateinit var is initialized
  • Overriding properties
  • Delegated properties

Interfaces

  • Implementing interfaces
  • Properties in interfaces
  • Interfaces Inheritance
  • Resolving overriding conflicts

Functional (SAM) interfaces

  • SAM conversions
  • Migration from an interface with constructor function to a functional interface
  • Functional interfaces vs. type aliases

Visibility modifiers

  • Packages
  • Class members
    • Constructors
    • Local declarations
  • Modules

Extensions

  • Extension functions
  • Extensions are resolved statically
  • Nullable receiver
  • Extension properties
  • Companion object extensions
  • Scope of extensions
  • Declaring extensions as members
  • Note on visibility

Data classes

  • Properties declared in the class body
  • Copying
  • Data classes and destructuring declarations
  • Standard data classes

Sealed classes and interfaces

  • Location of direct subclasses
    • Inheritance in multiplatform projects
  • Sealed classes and when expression

Generics: in, out, where

  • Variance
    • Declaration-site variance
  • Type projections
    • Use-site variance: type projections
    • Star-projections
  • Generic functions
  • Generic constraints
    • Upper bounds
  • Definitely non-nullable types
  • Type erasure
    • Generics type checks and casts
    • Unchecked casts
  • Underscore operator for type arguments

Nested and inner classes

  • Inner classes
  • Anonymous inner classes

Enum classes

  • Anonymous classes
  • Implementing interfaces in enum classes
  • Working with enum constants

Inline value classes

  • Members
  • Inheritance
  • Representation
    • Mangling
    • Calling from Java code
  • Inline classes vs type aliases
  • Inline classes and delegation

Object expressions and declarations

  • Object expressions
    • Creating anonymous objects from scratch
    • Inheriting anonymous objects from supertypes
    • Using anonymous objects as return and value types
    • Accessing variables from anonymous objects
  • Object declarations
    • Data objects
    • Companion objects
    • Semantic difference between object expressions and declarations

Delegation

  • Overriding a member of an interface implemented by delegation

Delegated properties

  • Standard delegates
    • Lazy properties
    • Observable properties
  • Delegating to another property
  • Storing properties in a map
  • Local delegated properties
  • Property delegate requirements
  • Translation rules for delegated properties
    • Optimized cases for delegated properties
    • Translation rules when delegating to another property
  • Providing a delegate

Type aliases

5. Null safety

  • Nullable types and non-nullable types
  • Checking for null in conditions
  • Safe calls
  • Nullable receiver
  • Elvis operator
  • The !! operator
  • Safe casts
  • Collections of a nullable type

6. Equality

  • Structural equality
  • Referential equality
  • Floating-point numbers equality
  • Array equality

7. This expressions

  • Qualified this
  • Implicit this

8. Scope functions

  • Function selection
  • Distinctions
    • Context object: this or it
    • Return value
  • Functions
    • let
    • with
    • run
    • apply
    • also
  • takeIf and takeUnless

9. Destructuring declarations

  • Example: returning two values from a function
  • Example: destructuring declarations and maps
  • Underscore for unused variables
  • Destructuring in lambdas

10. Reflection

  • JVM dependency
  • Class references
    • Bound class references
  • Callable references
    • Function references
    • Property references
    • Interoperability with Java reflection
    • Constructor references
    • Bound function and property references
    • Bound constructor references

11. Time measurement

  • Calculate duration
    • Create duration
    • Get string representation
    • Convert duration
    • Compare duration
    • Break duration into components
  • Measure time
    • Measure code execution time
    • Mark moments in time
    • Measure differences in time
  • Time sources
    • Default time sources per platform
    • Create time source

12. Collections

  • Collection types
    • Collection
    • List
    • Set
    • Map
    • ArrayDeque

13. Opt-in requirements

  • Opt in to using API
    • Propagating opt-in
    • Non-propagating opt-in
  • Require opt-in for API
    • Create opt-in requirement annotations
    • Mark API elements
  • Opt-in requirements for pre-stable APIs

14. Annotations

  • Usage
  • Constructors
  • Instantiation
  • Lambdas
  • Annotation use-site targets
  • Java annotations
    • Arrays as annotation parameters
    • Accessing properties of an annotation instance
    • Ability to not generate JVM 1.8+ annotation targets
  • Repeatable annotations

15. Asynchronous programming techniques

  • Threading
  • Callbacks
  • Futures, promises, and others
  • Reactive extensions
  • CoRoutines

16. Collections bi' tık Advance a.k.a E.H.

Constructing collections

  • Construct from elements
  • Create with collection builder functions
  • Empty collections
  • Initializer functions for lists
  • Concrete type constructors
  • Copy
  • Invoke functions on other collections

Iterators

  • List iterators
  • Mutable iterators

Ranges and progressions

  • Progression

Sequences

  • Construct
    • From elements
    • From an Iterable
    • From a function
    • From chunks
  • Sequence operations
  • Sequence processing example
    • Iterable
    • Sequence

Collection operations overview

  • Extension and member functions
  • Common operations
  • Write operations

Collection transformation operations

  • Map
  • Zip
  • Associate
  • Flatten
  • String representation

Filtering collections

  • Filter by predicate
  • Partition
  • Test predicates

Plus and minus operators

Grouping

Retrieve collection parts

  • Slice
  • Take and drop
  • Chunked
  • Windowed

Retrieve single elements

  • Retrieve by position
  • Retrieve by condition
  • Retrieve with selector
  • Random element
  • Check element existence

Ordering

  • Natural order
  • Custom orders
  • Reverse order
  • Random order

Aggregate operations

  • Fold and reduce

Collection write operations

  • Adding elements
  • Removing elements
  • Updating elements

List-specific operations

  • Retrieve elements by index
  • Retrieve list parts
  • Find element positions
    • Linear search
    • Binary search in sorted lists
  • List write operations
    • Add
    • Update
    • Remove
    • Sort

Set-specific operations

Map-specific operations

  • Retrieve keys and values
  • Filter
  • Plus and minus operators
  • Map write operations
    • Add and update entries
    • Remove entries

17. CoRoutines bi' tık Advance a.k.a E.H.

Basics

  • Your first coroutine
    • Structured concurrency
  • Extract function refactoring
  • Scope builder
  • Scope builder and concurrency
  • An explicit job
  • Coroutines are light-weight

Shared mutable state and concurrency

  • The problem
  • Volatiles are of no help
  • Thread-safe data structures
  • Thread confinement fine-grained
  • Thread confinement coarse-grained
  • Mutual exclusion

Cancellation and timeouts

  • Cancelling coroutine execution
  • Cancellation is cooperative
  • Making computation code cancellable
  • Closing resources with finally
  • Run non-cancellable block
  • Timeout
  • Asynchronous timeout and resources

Composing suspending functions

  • Sequential by default
  • Concurrent using async
  • Lazily started async
  • Async-style functions
  • Structured concurrency with async

Coroutine context and dispatchers

  • Dispatchers and threads
  • Unconfined vs confined dispatcher
  • Debugging coroutines and threads
    • Debugging with IDEA
    • Debugging using logging
  • Jumping between threads
  • Job in the context
  • Children of a coroutine
  • Parental responsibilities
  • Naming coroutines for debugging
  • Combining context elements
  • Coroutine scope
    • Thread-local data

Asynchronous Flow

  • Representing multiple values
    • Sequences
    • Suspending functions
    • Flows
  • Flows are cold
  • Flow cancellation basics
  • Flow builders
  • Intermediate flow operators
    • Transform operator
    • Size-limiting operators
  • Terminal flow operators
  • Flows are sequential
  • Flow context
    • A common pitfall when using withContext
    • flowOn operator
  • Buffering
    • Conflation
    • Processing the latest value
  • Composing multiple flows
    • Zip
    • Combine
  • Flattening flows
    • flatMapConcat
    • flatMapMerge
    • flatMapLatest
  • Flow exceptions
    • Collector try and catch
    • Everything is caught
  • Exception transparency
    • Transparent catch
    • Catching declaratively
  • Flow completion
    • Imperative finally block
    • Declarative handling
    • Successful completion
  • Imperative versus declarative
  • Launching flow
    • Flow cancellation checks
  • Flow and Reactive Streams

Channels

  • Channel basics
  • Closing and iteration over channels
  • Building channel producers
  • Pipelines
  • Prime numbers with pipeline
  • Fan-out
  • Fan-in
  • Buffered channels
  • Channels are fair
  • Ticker channels

Coroutine exceptions handling

  • Exception propagation
  • CoroutineExceptionHandler
  • Cancellation and exceptions
  • Exceptions aggregation
  • Supervision
    • Supervision job
    • Supervision scope