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

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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

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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

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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

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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

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6. Equality

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

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7. This expressions

• Qualified this
• Implicit this

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8. Scope functions

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

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9. Destructuring declarations

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

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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

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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

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12. Collections

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

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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

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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

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15. Asynchronous programming techniques

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

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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

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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