an example of JEP 405: Record Patterns & Array Patterns (Preview)

RecordPatterns.java

record Point(int x, int y) {}
enum Color { RED, GREEN, BLUE }
record ColoredPoint(Point p, Color c) {}
record Rectangle(ColoredPoint upperLeft, ColoredPoint lowerRight) {}

static void printXCoordOfUpperLeftPointBeforePatterns(Rectangle r) {
    if (r == null) return;
    ColoredPoint ul = r.upperLeft();
    if (ul == null) return;
    Point p = ul.p();
    if (p == null) return;
    int x = p.x();
    System.out.println("Upper-left corner: " + x);
}

// with record patterns (future work)
static void printXCoordOfUpperLeftPointWithPatterns(Rectangle r) {
    if (r instanceof Rectangle(ColoredPoint(Point(var x, var y), var c), var lr)) {
        System.out.println("Upper-left corner: " + x);
    }
}