Java `record` (Introduced in Java 14)

Java record is a feature introduced in Java 14, designed to simplify class definitions—especially for Data Transfer Objects (DTOs) or simple data carriers.

A record is a special type of class that provides a concise way to declare immutable data objects and significantly reduces boilerplate code.

1. Basic Definition

A record is an immutable reference type that functions similarly to a regular class but provides several simplifications.

Java automatically generates:

A constructor
Getter methods
equals(), hashCode(), and toString() methods

Example

public record Person(String name, int age) {
}

This automatically provides:

public Person(String name, int age)
name() and age() accessor methods
Implementations of equals, hashCode, and toString

2. How to Use Java Records

2.1 Creating a `record` Object

public class Main {
    public static void main(String[] args) {
        Person person = new Person("John", 30);
        System.out.println(person.name());  // Output: John
        System.out.println(person.age());   // Output: 30
        System.out.println(person);         // Output: Person[name=John, age=30]
    }
}

2.2 Immutability

record fields are final and cannot be modified after creation.

// This will cause a compilation error
person.name = "Jane";  // ❌ Error: Cannot assign a value to final variable 'name'

2.3 Auto-generated `equals`, `hashCode`, and `toString`

These methods are generated based on all fields.

Person person1 = new Person("John", 30);
Person person2 = new Person("John", 30);

System.out.println(person1.equals(person2));            // true
System.out.println(person1.hashCode() == person2.hashCode()); // true
System.out.println(person1);                            // Output: Person[name=John, age=30]

3. Advantages and Features

Concise: Reduces boilerplate code
Immutable: Safer in concurrent/multithreaded environments
Auto-Generated Methods: equals, hashCode, toString, and accessors

4. Limitations

No Class Inheritance: Cannot extend other classes (implicitly extends java.lang.Record)
No Setters: Fields are final, cannot be reassigned
Limited Extensibility: You can add methods but not instance field modifiers

5. Using `record` with Interfaces

record types can implement interfaces:

interface Identifiable {
    String getId();
}

public record Person(String id, String name, int age) implements Identifiable {
    @Override
    public String getId() {
        return id;
    }
}

6. Summary

Feature	Description
Immutable Fields	Fields are final and cannot be changed after creation
Auto-generated Methods	Constructor, accessors, `equals`, `hashCode`, `toString`
No Inheritance	Cannot extend classes, but can implement interfaces
Use Case	Great for DTOs and simple data-holding structures

Java record is ideal for:

Data Transfer Objects (DTOs)
Lightweight data holders
Reducing repetitive code
Improving code readability and maintainability

Java record (Introduced in Java 14)