Records

Key points

• A record declares data in one line: record Point(int x, int y) {}.
• You get the constructor, accessors, equals, hashCode and toString for free.
• Accessors are named x(), not getX(), and the fields are final — a record never changes after construction.
• The compact constructor Point { ... } validates or normalises the arguments before the fields are assigned.
• Records can add methods and static factories, but cannot extend a class. They are implicitly final.
• Ideal for DTOs, map keys and multi-value returns. Not a replacement for classes with real behaviour.

Example

import java.util.List;

public class Main {

    record Point(int x, int y) {
        Point {
            if (x < 0 || y < 0) throw new IllegalArgumentException("negative: " + x + "," + y);
        }

        double distanceFromOrigin() { return Math.sqrt(x * x + y * y); }

        static Point origin() { return new Point(0, 0); }
    }

    public static void main(String[] args) {
        Point p = new Point(3, 4);
        System.out.println("toString for free: " + p);
        System.out.println("accessor p.x() = " + p.x() + ", distance = " + p.distanceFromOrigin());
        System.out.println("equals by value: " + p.equals(new Point(3, 4)));
        System.out.println("same hashCode:   " + (p.hashCode() == new Point(3, 4).hashCode()));
        System.out.println("static factory:  " + Point.origin());
        System.out.println("in a list: " + List.of(p, new Point(1, 1)));

        try {
            new Point(-1, 0);
        } catch (IllegalArgumentException e) {
            System.out.println("compact constructor validated: " + e.getMessage());
        }
    }
}

Records give value semantics for free — use them for plain data.