أنماط Record المتداخلة

أنماط السجلات المتداخلة

نموذج بيانات متداخل

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}

    public static void main(String[] args) {
        Line line = new Line(new Point(0, 0), new Point(3, 4));
        System.out.println(line);
    }
}

فك البنية على مستوى واحد

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}

    public static void main(String[] args) {
        Object obj = new Line(new Point(0, 0), new Point(3, 4));
        if (obj instanceof Line(Point s, Point e)) {
            System.out.println(s + " -> " + e);
        }
    }
}

التعمق أكثر

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}

    public static void main(String[] args) {
        Object obj = new Line(new Point(0, 0), new Point(3, 4));
        if (obj instanceof Line(Point(int x1, int y1), Point(int x2, int y2))) {
            double len = Math.hypot(x2 - x1, y2 - y1);
            System.out.println("Length: " + len);
        }
    }
}

أي عمق

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}
    record Drawing(Line first, String label) {}

    public static void main(String[] args) {
        Object obj = new Drawing(new Line(new Point(1, 2), new Point(3, 4)), "diag");
        if (obj instanceof Drawing(Line(Point(var ax, var ay), var end), var label)) {
            System.out.println(label + " starts at " + ax + "," + ay);
            System.out.println("ends near " + end);
        }
    }
}

الدمج بين var والأنواع

التداخل في switch

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}

    static String describe(Object o) {
        return switch (o) {
            case Line(Point(var x1, var y1), Point(var x2, var y2)) when x1 == x2 -> "vertical";
            case Line(Point p1, Point p2) -> "general line";
            default -> "not a line";
        };
    }

    public static void main(String[] args) {
        System.out.println(describe(new Line(new Point(2, 0), new Point(2, 9))));
        System.out.println(describe(new Line(new Point(0, 0), new Point(5, 5))));
    }
}

يجب أن تنجح المطابقة كاملةً

موازنة قابلية القراءة

الحواجز فوق الإسنادات المتداخلة

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}

    static boolean isUnitStep(Object o) {
        return o instanceof Line(Point(int x1, int y1), Point(int x2, int y2))
            && x2 - x1 == 1 && y2 - y1 == 1;
    }

    public static void main(String[] args) {
        System.out.println(isUnitStep(new Line(new Point(0, 0), new Point(1, 1))));
        System.out.println(isUnitStep(new Line(new Point(0, 0), new Point(2, 2))));
    }
}

مثال كامل

public class Main {
    record Point(int x, int y) {}
    record Line(Point start, Point end) {}

    static Point midpoint(Object o) {
        if (o instanceof Line(Point(int x1, int y1), Point(int x2, int y2))) {
            return new Point((x1 + x2) / 2, (y1 + y2) / 2);
        }
        return null;
    }

    public static void main(String[] args) {
        System.out.println(midpoint(new Line(new Point(0, 0), new Point(4, 6))));
    }
}

اختبار سريع

مراجعة