How has sealed classes changed in recent Java versions?

Sealed classes in Java were introduced as a preview feature in Java 15 and became a standard feature in Java 17. They allow developers to define classes with strict control over which other classes can inherit from them, enhancing type safety and maintainability in large codebases.

With recent updates, the features surrounding sealed classes have been refined, including better error messages and expanded capabilities for interfaces.

sealed interface Shape permits Circle, Square {}

final class Circle implements Shape {
    // implementation details
}

final class Square implements Shape {
    // implementation details
}