Record Classes

Introduced in Java 16, Record Classes are special immutable classes designed to act as transparent data carriers, eliminating boilerplate getter, hashCode, equals, and toString definitions.

Record Architecture and Rules

• Immutability: All header fields compile into private final instance fields. Accessor methods match field names (e.g. user.email(), not getUserEmail()).
• Inheritance Restriction: Records are implicitly final. They cannot extend another class, and no other class can extend them. They can, however, implement interfaces.
• Compact Constructors: Allows writing validation logic without redeclaring parameters and assignments (fields are assigned automatically at the end of the block).

Code Walkthrough

This program demonstrates a Record declaration with a compact constructor validation check.

public class RecordDemo {
    public record User(String email, int age) {
        // Compact Constructor: parameters are implicit
        public User {
            if (email == null || email.isBlank()) {
                throw new IllegalArgumentException("Email required");
            }
        }
    }
public static void main(String[] args) {
        User user = new User("alice@example.com", 28);
        System.out.println(user); // Auto-generated toString()
        System.out.println("Email: " + user.email()); // Accessor method
    }
}

Interview-Relevant Information