21. Record Classes: Finality & Inheritance

The Scenario

Record classes were introduced to model plain data carriers. However, they have very strict rules regarding inheritance to ensure their "immutability" and "transparency" are preserved.

Predict what happens when we try to make a Record extend a class, or a class extend a Record.

class Base {
    void show() { System.out.println("Base"); }
}

// Case 1: Record extending a class
// record Person(String name) extends Base { } 

// Case 2: Class extending a record
record User(String id) { }
// class Admin extends User { } 

public class Main {
    public static void main(String[] args) {
        User u = new User("123");
        System.out.println(u.id());
        System.out.println(u instanceof Record);
    }
}

Take Your Shot

Predicted Output

Type exactly what you think will be printed in the console.