# classes Published articles for classes. This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles. ## New in Symfony 8.2: Attribute-based Forms DevFeed: [New in Symfony 8.2: Attribute-based Forms]() Original publisher: [Read original article]() Author: Javier Eguiluz Published: 2026-09-17T07:04:00Z Content type: release Language: en Sources: [Symfony Blog]() Topics: [Forms](), [Symfony](), [PHP](), [container](), [classes](), [enums]() Tags: [classes](), [container](), [enums](), [forms](), [php](), [symfony]() ### AI overview Symfony 8.2 adds PHP attributes for defining uncomplicated form types directly on DTO classes and properties. Symfony converts these attributes into regular form type services during container compilation, while more complex behavior remains the responsibility of form type extensions. ### Source excerpt Contributed by Benjamin Georgeault in #60563... ## Episode 68 "Operator Overloading with Type Classes" \[AtA\] DevFeed: [Episode 68 "Operator Overloading with Type Classes" \[AtA\]]() Original publisher: [Read original article]() Author: Nicolai Parlog Published: 2026-08-27T00:00:00Z Content type: article Language: en Sources: [Inside Java]() Topics: [Java](), [openjdk](), [Programming]() Tags: [classes](), [java](), [java-language](), [openjdk](), [project-valhalla](), [valhalla]() ### AI overview An Ask the Architects episode discusses how OpenJDK's Project Valhalla is improving Java's support for custom numerical types, including possible limited operator overloading for custom value types. ### Source excerpt How OpenJDK's Project Valhalla is improving Java's support for custom numerical types. ## 12 OOP Concepts EVERY Developer Should Know DevFeed: [12 OOP Concepts EVERY Developer Should Know]() Original publisher: [Read original article]() Author: Ashish Pratap Singh Published: 2026-02-12T04:27:26Z Content type: tutorial Language: en Sources: [AlgoMaster Newsletter]() Topics: [Object-oriented programming (OOP)](), [Programming](), [Code](), [interfaces](), [Polymorphism](), [App]() Tags: [class](), [classes](), [code](), [concepts](), [developer](), [interface](), [interfaces](), [object-oriented](), [oop](), [practical](), [programming](), [real-world]() ### AI overview An introductory tutorial on object-oriented programming explains how classes, objects, and interfaces organize state and behavior. It uses real-world examples such as users, orders, payments, and payment gateways, and notes that these concepts are relevant to low-level design interviews. ### Source excerpt Key Object-Oriented Programming Concepts ## Creating an Arduino Library for ESP32 DevFeed: [Creating an Arduino Library for ESP32]() Original publisher: [Read original article]() Author: John Lee Published: 2025-12-15T00:00:00Z Content type: tutorial Language: en Sources: [Blog on Developer Portal]() Topics: [Arduino](), [ESP32](), [Library](), [Development](), [Code](), [C++](), [ide](), [Programming](), [API]() Tags: [arduino](), [arduino-ide](), [beginner](), [blog](), [c-plus-plus](), [class](), [classes](), [code](), [development](), [esp32](), [getting-started](), [guide](), [how-to](), [ide](), [libraries](), [library](), [maintainability](), [modular](), [modularity](), [modules](), [programming](), [structure](), [tutorial]() ### AI overview A step-by-step guide to creating, structuring, and publishing custom Arduino libraries for ESP32. It explains library benefits and structure, prerequisites, and implementation through a minimal "Hello World" example. ### Source excerpt Learn how to create, structure, and publish Arduino libraries for ESP32. This step-by-step guide covers everything from understanding a library structure to submitting your library to the Arduino Library Manager. ## Embedded records - extracting data from classes DevFeed: [Embedded records - extracting data from classes]() Original publisher: [Read original article]() Author: Stephen Colebourne (noreply@blogger.com) Published: 2025-11-05T06:30:00Z Content type: article Language: en Sources: [Stephen Colebourne]() Topics: [Java](), [data]() Tags: [classes](), [data](), [java](), [javaideas](), [serialization]() ### AI overview The article discusses embedded records, a proposal to extend the benefits of Java records to classes that represent data. It addresses the gap between records and classes and mentions possible relevance to Serialization 2.0. ### Source excerpt At Devoxx Belgium 2025 I discussed the idea of embedded records with a few people. The idea is to take what is great about records, and extend that to classes that represent data. This responds to a pain point in Java, where there is a bit of a cliff-edge between records and classes. While millions of classes could and should be converted to records, millions more cannot. Yet they still represent data, and it would be a Good Thing to be able to capture that. Especially with Serialization 2.0 on the horizon. Please see the proposal document for more details. ## Six Principles for Writing Clean, Maintainable Classes DevFeed: [Six Principles for Writing Clean, Maintainable Classes]() Original publisher: [Read original article]() Author: Daniel Moka Published: 2025-04-19T05:00:55Z Content type: tutorial Language: en Sources: [Craft Better Software]() Topics: [clean-code](), [Code](), [Development](), [implementation](), [Inheritance]() Tags: [classes](), [clean-code](), [code](), [implementation](), [inheritance](), [quality](), [reuse]() ### AI overview This tutorial presents six principles for writing clean classes: use noun-based names, avoid unnecessary getters and setters, hide internal state, expose a focused API, order methods by call flow, and favor composition over inheritance. It argues that small, focused, intention-revealing classes are easier to change, test, and understand. ### Source excerpt 7 essential tips to produce maintainable and intention-revealing classes ## Generics DevFeed: [Generics]() Original publisher: [Read original article]() Author: author@typealias.com (Dave Leeds) Published: 2024-03-26T00:00:00Z Content type: tutorial Language: en Sources: [Dave Leeds on Kotlin - typealias.com]() Topics: [generics](), [Kotlin]() Tags: [classes](), [collections](), [enum-class](), [function](), [generics](), [introduction](), [kotlin](), [kotlin-generic-function](), [kotlin-generics](), [kotlin-parameterized-types](), [kotlin-type-argument](), [kotlin-type-erasure](), [kotlin-type-parameter](), [kotlin-type-parameter-constraint](), [kotlin-type-safety](), [learn-to-program](), [list](), [map](), [pair](), [programming]() ### AI overview A tutorial introducing Kotlin generics through collection types such as List, Pair, and Map, using a beverage-menu example with classes and an enum class. ### Source excerpt All the way back in Chapter 8, when we introduced collections, we saw our first generic type: List ... then we saw more generics in Chapter 9 when we looked at the Pair and Map classes. In order to stay focused on learning about collection types, we glossed over the details about these classes. Well, we've put off learning about them for long enough! It's finally time for us to gain a full understanding of generics, so buckle up! ## Generics in Kotlin DevFeed: [Generics in Kotlin]() Original publisher: [Read original article]() Published: 2024-03-18T00:01:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [generics](), [Kotlin](), [Type Parameter](), [Programming](), [classes](), [function](), [interfaces](), [kotlin compiler]() Tags: [classes](), [functions](), [generics](), [interfaces](), [kotlin](), [kotlin-compiler](), [programming](), [type-parameter](), [workshop-learning-programming]() ### AI overview This tutorial explains how generics work in Kotlin. It covers generic functions, classes, and interfaces, including type parameters, type arguments, explicit specification, compiler inference, and relationships between argument and result types. ### Source excerpt The essence of how generics work in Kotlin. ## What is CoroutineContext and how does it work? DevFeed: [What is CoroutineContext and how does it work?]() Original publisher: [Read original article]() Published: 2024-03-04T00:00:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [kotlin-coroutines](), [Kotlin](), [context](), [interface]() Tags: [classes](), [context](), [interface](), [kotlin](), [kotlin-coroutines](), [workshop-learning-programming]() ### AI overview This tutorial explains CoroutineContext as an indexed set of coroutine context elements. It covers combining elements, retrieving them by key or square-bracket syntax, and the role of companion objects as keys in kotlinx.coroutines. ### Source excerpt A deep explanation of the coroutine context - the powerful data holder for coroutines. ## Item 26: Use abstraction to protect code against changes DevFeed: [Item 26: Use abstraction to protect code against changes]() Original publisher: [Read original article]() Published: 2024-02-26T00:00:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [abstraction](), [Code](), [Software Engineering]() Tags: [abstraction](), [classes](), [code](), [database](), [display](), [password](), [software-engineering](), [sorting](), [threads](), [validation](), [workshop-learning-programming]() ### AI overview This tutorial explains how abstraction protects code from changes. It covers extracting literal values into constants, separating algorithms into functions, and using abstractions to change implementation details without changing how code is used. ### Source excerpt How do we abstract elements, and what are the consequences. ## Sealed Types DevFeed: [Sealed Types]() Original publisher: [Read original article]() Author: author@typealias.com (Dave Leeds) Published: 2024-01-16T00:00:00Z Content type: tutorial Language: en Sources: [Dave Leeds on Kotlin - typealias.com]() Topics: [Kotlin](), [interfaces]() Tags: [classes](), [enum](), [exhaustive](), [exhaustive-matching](), [interfaces](), [introduction](), [kotlin](), [learn-to-program](), [programming](), [sealed](), [sealed-class](), [sealed-interface](), [subtype](), [types](), [when-conditional](), [when-expression]() ### AI overview A tutorial chapter explains how Kotlin sealed interfaces and classes restrict the set of possible types, helping ensure that all possibilities are handled in a when expression. ### Source excerpt In Chapter 5, we saw how limiting our options can be a good thing. In that chapter, we used enum classes to limit our values, which allows Kotlin to ensure that we account for all possibilities in a when expression. We can get a similar benefit for our types by using sealed interfaces and classes. In this chapter, we'll visit Cecil's Ice Shop to learn all about sealed types. Let's get started! ## Data classes in Kotlin DevFeed: [Data classes in Kotlin]() Original publisher: [Read original article]() Published: 2023-11-13T00:01:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [Kotlin](), [classes](), [data]() Tags: [classes](), [code](), [data-class](), [kotlin](), [type](), [workshop-learning-programming]() ### AI overview This tutorial explains Kotlin data classes, including how they differ from regular classes and how the compiler generates methods such as equals, hashCode, toString, and component functions. It also discusses inherited object behavior and when custom overrides are typically unnecessary. ### Source excerpt What are data classes in Kotlin and how do we use them. ## Effective Kotlin Item 48: Consider using object declarations DevFeed: [Effective Kotlin Item 48: Consider using object declarations]() Original publisher: [Read original article]() Published: 2023-11-06T00:00:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [Kotlin](), [object](), [classes](), [Kotlin programming]() Tags: [classes](), [consider](), [effective](), [instead](), [kotlin](), [object](), [regular](), [using](), [workshop-learning-programming]() ### AI overview This tutorial explains when to use Kotlin object declarations instead of regular classes, including the covariant Nothing object pattern for generic types. ### Source excerpt Why we should use object declarations instead of regular classes. ## Kotlin Reflection: Method and property references DevFeed: [Kotlin Reflection: Method and property references]() Original publisher: [Read original article]() Published: 2023-10-16T00:15:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [Kotlin](), [Programming](), [classes](), [function](), [properties]() Tags: [classes](), [dependency-injection](), [functions](), [gson](), [interfaces](), [java](), [koin](), [kotlin](), [property](), [workshop-learning-programming]() ### AI overview This tutorial introduces Kotlin reflection, explaining how programs inspect classes, functions, properties, annotations, constructors, and other source-code elements at runtime. It also describes uses in Gson serialization, Koin dependency injection, and the hierarchy of Kotlin reflection reference types. ### Source excerpt The general hierarchy of Kotlin reference classes, and details about method and property references. ## Sealed Generics and SKIE - Paul Hawke DevFeed: [Sealed Generics and SKIE - Paul Hawke]() Original publisher: [Read original article]() Published: 2023-10-10T00:00:00Z Content type: tutorial Language: en Sources: [Touchlab | Enterprise Mobile Innovation & Development]() Topics: [Kotlin](), [generics](), [Swift](), [classes](), [Xcode]() Tags: [apis](), [classes](), [generics](), [kmp](), [kotlin](), [kotlin-multiplatform](), [sealed](), [sealed-classes](), [skie](), [swift](), [type](), [xcode]() ### AI overview This tutorial explores how SKIE improves the use of Kotlin sealed classes with generics when exposing Kotlin Multiplatform code to Swift. It discusses type discovery in Xcode, Swift interoperability, and concurrency-related code paths. ### Source excerpt Sealed Classes and Generics are both very useful for Kotlin APIs, and very painful with KMP and Swift. One of SKIE's lesser known benefits is the restoration of using Sealed Classes with generics, along with proper type discovery in Xcode. ## Data Classes and Destructuring DevFeed: [Data Classes and Destructuring]() Original publisher: [Read original article]() Author: author@typealias.com (Dave Leeds) Published: 2023-10-09T00:00:00Z Content type: tutorial Language: en Sources: [Dave Leeds on Kotlin - typealias.com]() Topics: [Kotlin](), [data]() Tags: [class](), [classes](), [copy](), [data-class](), [destructuring](), [destructuring-assignment](), [equals](), [hashcode](), [introduction](), [kotlin](), [learn-to-program](), [object](), [open](), [operator](), [override](), [programming](), [properties](), [tostring]() ### AI overview A Kotlin tutorial introducing data classes and destructuring. It explains how data classes relate to equals(), hashCode(), and toString(), beginning with reference equality and overriding inherited functions. ### Source excerpt At the end of the last chapter, we saw how all objects in Kotlin inherit three functions from an open class called Any. Those functions are equals(), hashCode(), and toString(). In this chapter, we're going to learn about data classes, which are super-powered classes that are especially helpful when we've got an immutable class that mainly just holds properties. To better understand data classes, let's first explore each of the three functions above, and see what's involved when we override them! ## Abstract and Open Classes DevFeed: [Abstract and Open Classes]() Original publisher: [Read original article]() Author: author@typealias.com (Dave Leeds) Published: 2023-08-21T00:00:00Z Content type: tutorial Language: en Sources: [Dave Leeds on Kotlin - typealias.com]() Topics: [Code](), [interfaces]() Tags: [abstract-class](), [classes](), [compare](), [delegation](), [extend](), [function](), [implement](), [inheritance](), [interface](), [interfaces](), [introduction](), [kotlin](), [learn-to-program](), [open-class](), [polymorphism](), [programming](), [retro](), [speed](), [subclass](), [superclass]() ### AI overview A tutorial chapter explaining how to extend open and abstract classes to create subtypes and share general code. It compares this approach with interfaces and delegation, highlighting that each has advantages and disadvantages. ### Source excerpt In Chapter 12, we saw how we could use interfaces to create subtypes, and in the last chapter, we saw how we could use delegation with interfaces in order to share general code among specific classes. In this chapter, we'll learn how we can extend open and abstract classes to accomplish these same things with a different approach. Each approach has its advantages and disadvantages, so we'll also look at how they compare to one another. ## Avoid Java double brace initialization DevFeed: [Avoid Java double brace initialization]() Original publisher: [Read original article]() Author: Pierre-Yves Ricau Published: 2023-06-27T20:58:00Z Content type: tutorial Language: en Sources: [Py's blog]() Topics: [Java](), [Code](), [Android]() Tags: [android](), [class](), [classes](), [code](), [constructor](), [crash-reporting](), [gc](), [global](), [implementation](), [java](), [leak](), [leakcanary](), [lifecycle](), [memory](), [memory-leak](), [object](), [patterns](), [subclass]() ### AI overview This tutorial explains how Java double brace initialization can cause memory leaks. An anonymous HashMap subclass implicitly retains its outer Activity, so a breadcrumb stored by a singleton BugSnag client can keep a destroyed Android Activity in memory. The article recommends avoiding the pattern and using explicit initialization or Kotlin. ### Source excerpt TL;DR Avoid doing this: new HashMap() {{ put("key", value); }}; Leak Trace I was recently looking at the following leak trace from LeakCanary: ┬─── │ GC Root: Global variable in native code │ ├─ com.bugsnag.android.AnrPlugin instan... ## Class Modifiers in Dart: Sealed, Interface, Base DevFeed: [Class Modifiers in Dart: Sealed, Interface, Base]() Original publisher: [Read original article]() Author: Marvin März Published: 2023-06-23T11:29:43Z Content type: tutorial Language: en Sources: [QuickBird Studios Blog]() Topics: [Dart](), [Object-oriented programming (OOP)]() Tags: [abstract-class](), [class](), [classes](), [dart](), [flutter](), [implementation](), [interface](), [oop](), [pattern-matching](), [post](), [sealed](), [sealed-interface]() ### AI overview This tutorial explains Dart 3 class modifiers, including the newly introduced sealed, interface, final, and base modifiers and changes to existing modifiers. It describes how modifiers control whether classes can be extended, mixed in, constructed, or implemented, and discusses their practical use cases. ### Source excerpt With Dart 3 the class modifiers sealed, interface, final and base were introduced into the Dart language. They also updated how existing ones work. In this article, we show you why this change was made and how those new modifiers work. The post Class Modifiers in Dart: Sealed, Interface, Base appeared first on QuickBird Studios. ## Java on-ramp - Fully defined Entrypoints DevFeed: [Java on-ramp - Fully defined Entrypoints]() Original publisher: [Read original article]() Author: Stephen Colebourne (noreply@blogger.com) Published: 2022-10-06T11:18:00Z Content type: opinion Language: en Sources: [Stephen Colebourne]() Topics: [Java](), [Code](), [openjdk]() Tags: [classes](), [code](), [getting-started](), [java](), [javaideas](), [launch]() ### AI overview The article argues that Java should introduce a dedicated entrypoint class declaration to make starting programs easier for newcomers and more useful for developers generally. The proposal would provide simpler syntax that compiles to a class file with distinct rules, including inferred class names and top-level code. ### Source excerpt How do you start a Java program? With a main method of course. But the ceremony around writing such a method is perhaps not the nicest for newcomers to Java. There has been a bit of dicussion recently about how the "on-ramp" for Java could be made easier. This is the original proposal. Here are follow ups - OpenJDK, Reddit, Hacker news. Starting point This is the classic Java Hello Word: public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World"); } } Lots of stuff going on - public, class, a class name, void, arrays, a method, method call. And one of the weirdest things in Java - System.out - a public static field in lower case. Something that is pretty much never seen in normal Java code. (I still remember System.out.println being the most confusing part about getting started in Java 1.0 - why are there two dots and why isn't it out()?) The official proposal continues to discuss: A more tolerant launch protocol Unnamed classes Predefined static imports for the most critical methods and fields The ensuing discussion resulted in various suggestions. Having taken some time to reflect on the proposal and discussion, here is my contribution, which is that what is really needed is something more comprehensive. Entrypoints When a Java program starts some kind of class file needs to be run. It could be a normal class, but that isn't ideal as we don't really want static/instance variables, subclasses, parent interfaces, access control etc. One suggestion was for it to be a normal interface, but that isn't ideal as we don't want to mark the methods as default or allow abstract methods. I'd like to propose that what Java needs is a new kind of class declaration for entrypoints. I don't think this is overly radical. We already have two alternate class declarations - record and enum. They have alternate syntax that compiles to a class file without being explictly a class in source code. What we need here is a new kind - entrypoint - tha ## Sealed classes in Kotlin DevFeed: [Sealed classes in Kotlin]() Original publisher: [Read original article]() Author: Florian Garcia Published: 2022-09-26T13:51:32Z Content type: tutorial Language: en Sources: [betclic-tech - Medium]() Topics: [Kotlin](), [interfaces](), [Inheritance](), [Code](), [Exception]() Tags: [classes](), [code](), [exception](), [inheritance](), [interfaces](), [kotlin](), [sealed](), [sealed-classes]() ### AI overview A tutorial explaining how Kotlin sealed classes and interfaces represent restricted class hierarchies. It shows how they help the compiler identify all supported cases and avoid missing-case handling when the hierarchy changes. ### Source excerpt In this article, we will talk about sealed classes and interfaces. What they are, what problem they solve and how we can leverage this in real life. The problem Let's take the following code: https://medium.com/media/f1f04b5ee8f0bfc98d41cad1fbd803a2/href Our code only handles two types of animals (cats and dogs). But the compiled code does not know that only those two types exist. This means we have to add this ugly else block in our when. This can be a real issue because you start to think about what to do in a situation that shouldn't exist but that will potentially exist in the future. For instance, say that tomorrow we add cows to the list of supported animals, the code will compile just fine because we have put the else block. We could change the else part to throw an exception but Kotlin does not have checked exceptions (so it's easy to forget to catch one), and thus we end up with runtime exceptions. That's a bit sad because we probably want to know at compile time that we need to handle this new case. Solution As you probably have guessed, the solution is sealed classes or interfaces. But what are they? From the Kotlin documentation: Sealed classes and interfaces represent restricted class hierarchies that provide more control over inheritance. All direct subclasses of a sealed class are known at compile time. No other subclasses may appear after a module with the sealed class is compiled. For example, third-party clients can't extend your sealed class in their code. Thus, each instance of a sealed class has a type from a limited set that is known when this class is compiled. If rephrased, this means that we can define a bounded hierarchy. One of the important things to know when working with sealed classes is that you cannot instantiate the sealed class; thus only the leaves of the structure exist at runtime (but you can use the interface as a type). When we develop applications that are not libraries, it is pretty rare to allow an abstract class / interfac ## Scopes and Scope Functions DevFeed: [Scopes and Scope Functions]() Original publisher: [Read original article]() Author: author@typealias.com (Dave Leeds) Published: 2022-08-22T00:00:00Z Content type: tutorial Language: en Sources: [Dave Leeds on Kotlin - typealias.com]() Topics: [Kotlin](), [Library](), [Code]() Tags: [also](), [apply](), [classes](), [code](), [introduction](), [kotlin](), [learn](), [learn-to-program](), [let](), [library](), [programming](), [run](), [scope](), [scope-function](), [scope-functions](), [shadowing](), [standard](), [standard-library](), [variable](), [visibility](), [with]() ### AI overview A Kotlin tutorial chapter introduces scopes as regions of code where variables, functions, and classes can be declared, then begins explaining Kotlin's five scope functions from the standard library. ### Source excerpt In the last chapter, we learned how to create extension functions, which can be called using dot notation. In this chapter, we'll learn about scope functions, which are five particular functions that Kotlin gives us in its standard library. Before we can understand scope functions, though, it helps to first understand scopes. Introduction to Scopes In Kotlin, a scope is a section of code where we can declare new variables, functions, classes, and more. ## Separate code from data DevFeed: [Separate code from data]() Original publisher: [Read original article]() Author: Yehonathan Sharvit Published: 2022-06-22T02:32:24Z Content type: tutorial Language: en Sources: [Klipse]() Topics: [Programming](), [Object-oriented programming (OOP)](), [classes]() Tags: [behavior](), [classes](), [code](), [d](), [data](), [dop](), [oop](), [programming]() ### AI overview This article explores the first principle of Data-Oriented Programming: separating code, or behavior, from data. It explains how the principle can be followed or violated in both object-oriented programming and functional programming, including examples involving classes, static methods, and lexical scope. ### Source excerpt The first principle of Data-Oriented Programming (DOP) is a design principle that recommends a clear separation between code (behavior) and data. This may appear to be a FP principle, but in fact, one can adhere to it or break it either in FP or in OOP: ## Effective Kotlin Item 52: Consider using inline value classes DevFeed: [Effective Kotlin Item 52: Consider using inline value classes]() Original publisher: [Read original article]() Published: 2021-09-06T00:00:00Z Content type: tutorial Language: en Sources: [Kt. Academy]() Topics: [Kotlin](), [class]() Tags: [classes](), [kotlin](), [using](), [value](), [workshop-learning-programming]() ### AI overview This tutorial explains Kotlin inline value classes, including how they can wrap a single value with little or no performance overhead. It covers using them to represent units of measure, prevent value misuse through types, and optimize memory usage. ### Source excerpt What value classes are, how to use and inline them. [Next page]()