Java Records: Modern Immutable Data Classes & Boilerplate Elimination

For decades, creating simple Data Transfer Objects (DTOs) or immutable value classes in Java required writing extensive repetitive boilerplate: private final fields, constructors, getters, equals(), hashCode(), and toString(). Java Records (finalized in Java 16 LTS) eliminate this friction entirely in a single line of code.

Traditional POJO vs. Modern Java Record

The Old Way: ~50 Lines of Boilerplate POJO:

// Old way: Painful and verbose
public final class StudentDto {
    private final int id;
    private final String name;
    private final String email;

    public StudentDto(int id, String name, String email) {
        this.id = id;
        this.name = name;
        this.email = email;
    }
    public int getId() { return id; }
    public String getName() { return name; }
    public String getEmail() { return email; }
    // ... plus 30 more lines of equals(), hashCode(), and toString()!
}

The Modern Java Way: Exactly 1 Line:

// Modern Java 16+ LTS: 100% equivalent in one line!
public record StudentDto(int id, String name, String email) {}

Using a Record in Action

Notice that record field accessors do NOT use the get prefix; they simply use the field name (e.g. student.name()):

public class RecordDemo {
    public static void main(String[] args) {
        StudentDto s1 = new StudentDto(101, "Aarav Sharma", "aarav@veewom.com");
        StudentDto s2 = new StudentDto(101, "Aarav Sharma", "aarav@veewom.com");

        // 1. Accessing fields via accessor methods:
        System.out.println("Student Name: " + s1.name());

        // 2. Built-in human-readable toString():
        System.out.println(s1); 
        // Output: StudentDto[id=101, name=Aarav Sharma, email=aarav@veewom.com]

        // 3. Built-in value-based equality comparison:
        System.out.println("s1 equals s2: " + s1.equals(s2)); // Output: true!
    }
}

Compact Constructors for Validation

To validate input parameters inside a record, define a Compact Constructor:

public record BankTransfer(String sender, String receiver, double amount) {
    // Compact Constructor (Notice no parameter list!)
    public BankTransfer {
        if (amount <= 0) {
            throw new IllegalArgumentException("Transfer amount must be positive!");
        }
        if (sender == null || receiver == null) {
            throw new NullPointerException("Parties cannot be null!");
        }
        // Automatic assignment occurs immediately after!
    }
}