/** * Run: `java --enable-preview --source 19 RecordPatternsTest.java` */ public class RecordPatternsTest { public static void main(String[] args) { simpleExampleOfDeconstruct(); var p1 = new Point(10, 10); var p2 = new ColoredPoint(new Point(10, 10), Color.GREEN); System.out.println("Has collision: " + checkCollisionIfs(p1, p2)); System.out.println("Has collision: " + checkCollisionSwitches(p1, p2)); } static void simpleExampleOfDeconstruct() { record ComputedPoint (int x, int y) { // the accessor method is used is the deconstruction public int y() { return this.y + 10; } } Object point = new ComputedPoint(42, 42); // `int x` will receive the result of implitcy accessor `Point.x()` // `int y` will receive the result of explicity accesor `Point.y()` if (point instanceof ComputedPoint(int x, var y)) { System.out.printf("Deconstruction: x=%d, y=%d%n%n", x, y); } else { System.out.println("Not a instance of ComputedPoint"); } } static boolean checkCollisionIfs(Object p1, Object p2) { if (p1 instanceof Point(int x1, int y1) && p2 instanceof Point(int x2, int y2)) { return x1 == x2 && y1 == y2; } if (p1 instanceof Point(int x1, int y1) && p2 instanceof ColoredPoint(Point(int x2, int y2), Color c)) { return x1 == x2 && y1 == y2; } if (p1 instanceof ColoredPoint(Point(int x1, int y1), Color c) && p2 instanceof Point(int x2, int y2)) { return x1 == x2 && y1 == y2; } if (p1 instanceof ColoredPoint(Point(int x1, int y1), Color c1) && p2 instanceof ColoredPoint(Point(int x2, int y2), Color c2)) { return x1 == x2 && y1 == y2; } throw new IllegalArgumentException("Invalid type"); } static boolean checkCollisionSwitches(Object p1, Object p2) { int x1, y1, x2, y2; // Record pattern on switch should be exhaustive (careful with generics on record) switch (p1) { case Point(int px1, int py1) -> { x1 = px1; y1 = py1; } case ColoredPoint(Point(int px1, int py1), Color c) -> { x1 = px1; y1 = py1; } case null, default -> throw new IllegalArgumentException("Invalid type"); } switch (p2) { case Point(int px2, int py2) -> { x2 = px2; y2 = py2; } case ColoredPoint(Point(int px2, int py2), Color c) -> { x2 = px2; y2 = py2; } case null, default -> throw new IllegalArgumentException("Invalid type"); } return x1 == x2 && y1 == y2; } } record Point(int x, int y) {} enum Color { RED, GREEN, BLUE } record ColoredPoint(Point p, Color c) {}