Java: What are records in Java 16+?

1public record Point(int x, int y) {
2    // Compact constructor for validation (no parameter assignment)
3    public Point {
4        if (x < 0 || y < 0) throw new IllegalArgumentException("Coordinates must be non-negative");
5    }
6
7    // Custom methods
8    public double distanceTo(Point other) {
9        return Math.sqrt(Math.pow(x - other.x, 2) + Math.pow(y - other.y, 2));
10    }
11
12    // Static factory method
13    public static Point origin() {
14        return new Point(0, 0);
15    }
16}
17
18// Auto-generates:
19// - Canonical constructor: Point(int x, int y)
20// - Accessor methods: x(), y() (not getX()!)
21// - equals(), hashCode(), toString()
22
23var p = new Point(3, 4);
24System.out.println(p.x());            // 3
25System.out.println(p.toString());     // Point[x=3, y=4]
26System.out.println(p.equals(new Point(3, 4))); // true

1// Records implementing interfaces
2public interface Shape {
3    double area();
4}
5
6public record Circle(double radius) implements Shape {
7    @Override
8    public double area() {
9        return Math.PI * radius * radius;
10    }
11}
12
13// Records with collections
14public record Team(String name, List<String> members) {
15    // Defensive copy in compact constructor
16    public Team {
17        members = List.copyOf(members); // Immutable copy
18    }
19}