Records

Syntax

record RecordName(type field1, type field2) { }

Examples

public record Point(int x, int y) { }

public class RecordExample {
    public static void main(String[] args) {
        Point p1 = new Point(3, 4);

        System.out.println(p1.x());          // 3 - auto-generated accessor
        System.out.println(p1.y());          // 4
        System.out.println(p1);               // Point[x=3, y=4] - auto toString()

        Point p2 = new Point(3, 4);
        System.out.println(p1.equals(p2));    // true - auto equals() compares fields
    }
}

public record Rectangle(double width, double height) {
    public double area() {
        return width * height;
    }

    public boolean isSquare() {
        return width == height;
    }
}

Rectangle r = new Rectangle(5, 5);
System.out.println(r.area());       // 25.0
System.out.println(r.isSquare());   // true

public record Temperature(double celsius) {
    public Temperature {  // compact constructor - no parameter list repeated
        if (celsius < -273.15) {
            throw new IllegalArgumentException("Below absolute zero!");
        }
    }

    public double toFahrenheit() {
        return celsius * 9 / 5 + 32;
    }
}

Temperature t = new Temperature(25);
System.out.println(t.toFahrenheit());  // 77.0

// new Temperature(-300);  // throws IllegalArgumentException

Best practices

• Use records for simple, immutable data carriers (DTOs, value objects) instead of hand-writing a full class with getters, equals, hashCode, and toString
• Add validation logic in a compact constructor to guarantee a record can never be created in an invalid state
• Remember records are implicitly final and all fields are final - they are not meant for classes that need mutable state or inheritance
• Use a record's auto-generated accessor methods (x(), y()) rather than adding your own getX()/getY() unless you specifically need JavaBean-style naming

At a glance

Purpose

General-purpose application development

File extension

.java

Runs in

Java Virtual Machine

Usually used with

JDK and Java libraries

Specifications & further reading

• Java Language Specification

Related Java documentation