Records
Records are Java classes which allows simple definition of immutable data
structures.
Since Java 16
public class Records {
record Point(double x, double y) {
// We can add additional methods
double dist(Point p2) {
var dx = x - p2.x;
var dy = y - p2.y;
return Math.sqrt(dx * dx + dy * dy);
}
}
interface Shape {
double area();
}
record Circle(Point center, double radius) implements Shape {
// we can add overloaded versions of the constructor
Circle(Point center, Point pointoncircle) {
this(center, center.dist(pointoncircle));
}
// we can implement an interface
@Override
public double area() {
return Math.PI * radius * radius;
}
}
public static void main(String[] args) {
var p = new Point(3, 5);
// We have
System.out.println(p.x());
// The compiler creates a toString() method for us
System.out.println(p);
// As well as equals() and hashcode() methods
System.out.println(p.equals(new Point(3, 5)));
System.out.println(p.hashCode());
var c = new Circle(p, new Point(6, 8));
System.out.println(c.area());
}
}
This snippet at GitHub
