What are the differences between a regular class, a data class, and a sealed class in the Kotlin programming language?

In Kotlin, there are different types of classes, each with its own features:

• Regular class (class) — a standard class that can be inherited (unless declared as final), contains properties and methods. It does not automatically generate equals(), hashCode(), toString() methods.

• Data class (data class) — a class designed for storing data. The compiler automatically generates equals(), hashCode(), toString(), as well as copy() and destructuring functions. Example:

data class User(val name: String, val age: Int)

• Sealed class (sealed class) — a class that restricts the inheritance hierarchy. All subclasses must be declared in the same file. Used to represent a limited set of types, often in when expressions to ensure exhaustiveness. Example:

sealed class Result {
    data class Success(val data: String) : Result()
    object Error : Result()
}

Thus:

• Regular class — versatile.
• Data class — for convenient storage and manipulation of data.
• Sealed class — for limited hierarchy and safe pattern matching.