# abstract class

An abstract class is an incomplete class intended as a base class that cannot be instantiated directly and may contain abstract members.

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## Sealed classes and interfaces in Kotlin

DevFeed: [Sealed classes and interfaces in Kotlin](<https://devfeed.tech/articles/sealed-classes-and-interfaces-in-kotlin-39339.md>)

Original publisher: [Read original article](<https://kt.academy/article/kfde-sealed>)

Published: 2023-09-04T00:01:00Z

Content type: tutorial

Language: en

Sources: [Kt. Academy](<https://devfeed.tech/sources/kt-academy.md>)

Topics: [Kotlin](<https://devfeed.tech/topics/kotlin.md>), [sealed class](<https://devfeed.tech/topics/sealed-class.md>), [sealed interface](<https://devfeed.tech/topics/sealed-interface.md>), [interface](<https://devfeed.tech/topics/interface.md>), [abstract class](<https://devfeed.tech/topics/abstract-class.md>), [Inheritance](<https://devfeed.tech/topics/inheritance.md>), [Polymorphism](<https://devfeed.tech/topics/polymorphism.md>)

Tags: [inheritance](<https://devfeed.tech/tags/inheritance.md>), [interface](<https://devfeed.tech/tags/interface.md>), [kotlin](<https://devfeed.tech/tags/kotlin.md>), [polymorphism](<https://devfeed.tech/tags/polymorphism.md>), [sealed](<https://devfeed.tech/tags/sealed.md>), [sealed-classes](<https://devfeed.tech/tags/sealed-classes.md>), [sealed-interface](<https://devfeed.tech/tags/sealed-interface.md>), [workshop-learning-programming](<https://devfeed.tech/tags/workshop-learning-programming.md>)

### AI overview

This Kotlin tutorial explains sealed classes and sealed interfaces as restricted hierarchies whose direct subclasses are controlled. It contrasts them with regular interfaces and abstract classes, describes their package and module requirements, and explains their use in exhaustive expressions.

### Source excerpt

What are sealed classes and interfaces in Kotlin and how do we use them.

## Design Patterns: Builder

DevFeed: [Design Patterns: Builder](<https://devfeed.tech/articles/design-patterns-builder-40673.md>)

Original publisher: [Read original article](<https://radek.io/posts/design-patterns-builder/>)

Published: 2011-08-02T00:00:00Z

Content type: tutorial

Language: en

Sources: [Radek Pazdera](<https://devfeed.tech/sources/radek-pazdera.md>)

Topics: [Architecture & Design](<https://devfeed.tech/topics/architecture-design.md>), [Software](<https://devfeed.tech/topics/software.md>), [Software Engineering](<https://devfeed.tech/topics/software-engineering.md>), [abstract class](<https://devfeed.tech/topics/abstract-class.md>), [interface](<https://devfeed.tech/topics/interface.md>)

Tags: [abstract-class](<https://devfeed.tech/tags/abstract-class.md>), [build](<https://devfeed.tech/tags/build.md>), [builder](<https://devfeed.tech/tags/builder.md>), [class](<https://devfeed.tech/tags/class.md>), [constructor](<https://devfeed.tech/tags/constructor.md>), [design-patterns](<https://devfeed.tech/tags/design-patterns.md>), [example](<https://devfeed.tech/tags/example.md>), [interface](<https://devfeed.tech/tags/interface.md>), [object](<https://devfeed.tech/tags/object.md>), [software-design](<https://devfeed.tech/tags/software-design.md>)

### AI overview

This tutorial explains the Builder design pattern as a creational pattern that moves complex object construction into a separate builder and director structure. It uses assembling different types of cars as an example.

### Source excerpt

Software design patterns by example

## Design Patterns: Abstract Factory

DevFeed: [Design Patterns: Abstract Factory](<https://devfeed.tech/articles/design-patterns-abstract-factory-40670.md>)

Original publisher: [Read original article](<https://radek.io/posts/design-patterns-abstract-factory/>)

Published: 2011-07-24T00:00:00Z

Content type: tutorial

Language: en

Sources: [Radek Pazdera](<https://devfeed.tech/sources/radek-pazdera.md>)

Topics: [Architecture & Design](<https://devfeed.tech/topics/architecture-design.md>), [abstract class](<https://devfeed.tech/topics/abstract-class.md>), [Software](<https://devfeed.tech/topics/software.md>), [class](<https://devfeed.tech/topics/class.md>), [classes](<https://devfeed.tech/topics/classes.md>), [ui](<https://devfeed.tech/topics/ui.md>), [Code](<https://devfeed.tech/topics/code.md>), [coding](<https://devfeed.tech/topics/coding.md>), [Linux](<https://devfeed.tech/topics/linux.md>), [Qt](<https://devfeed.tech/topics/qt.md>), [GTK](<https://devfeed.tech/topics/gtk.md>), [Windows](<https://devfeed.tech/topics/windows.md>)

Tags: [abstract-class](<https://devfeed.tech/tags/abstract-class.md>), [code](<https://devfeed.tech/tags/code.md>), [components](<https://devfeed.tech/tags/components.md>), [design](<https://devfeed.tech/tags/design.md>), [design-patterns](<https://devfeed.tech/tags/design-patterns.md>), [desktop](<https://devfeed.tech/tags/desktop.md>), [example](<https://devfeed.tech/tags/example.md>), [gnome](<https://devfeed.tech/tags/gnome.md>), [interface](<https://devfeed.tech/tags/interface.md>), [interface-design](<https://devfeed.tech/tags/interface-design.md>), [kde](<https://devfeed.tech/tags/kde.md>), [linux](<https://devfeed.tech/tags/linux.md>), [object](<https://devfeed.tech/tags/object.md>), [patterns](<https://devfeed.tech/tags/patterns.md>), [platform](<https://devfeed.tech/tags/platform.md>), [software](<https://devfeed.tech/tags/software.md>), [software-design](<https://devfeed.tech/tags/software-design.md>), [ui](<https://devfeed.tech/tags/ui.md>), [ui-components](<https://devfeed.tech/tags/ui-components.md>), [user-interface](<https://devfeed.tech/tags/user-interface.md>)

### AI overview

This tutorial explains the Abstract Factory design pattern, which encapsulates the creation of related families of objects without specifying their concrete classes. It uses a cross-platform user-interface example in which separate factories create components for KDE/Qt and GNOME/Gtk environments.

### Source excerpt

Software design patterns by example