Java Sealed Classes

Restrict which other classes or interfaces may extend or implement them.

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Introduced in Java 17, sealed classes provide finer-grained control over inheritance than final by explicitly specifying subclasses via the permits keyword.

Key Takeaways: Java Sealed Classes

Mastering Java Sealed Classes helps you write clean and reliable Java code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

Java Sealed Classes Code Example

Java

public sealed interface Shape permits Circle, Square {}

final class Circle implements Shape {}
final class Square implements Shape {}

public class Main {
    public static void main(String[] args) {
        Shape s = new Circle();
        System.out.println("Sealed shape instantiated: " + s.getClass().getSimpleName());
    }
}

Output

Sealed shape instantiated: Circle

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Java Sealed Classes

💡 Key Takeaways: Java Sealed Classes

Java Sealed Classes Code Example

Key Takeaways: Java Sealed Classes