instanceof के लिए पैटर्न मिलान

public class Main {
    public static void main(String[] args) {
        Object obj = "hello";
        if (obj instanceof String) {
            String s = (String) obj;
            System.out.println(s.length());
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Object obj = "hello";
        if (obj instanceof String s) {
            System.out.println(s.length());
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Object obj = "developer";
        if (obj instanceof String s && s.length() > 5) {
            System.out.println("Long string: " + s);
        }
    }
}

public class Main {
    static int safeLength(Object obj) {
        if (!(obj instanceof String s)) {
            return -1;
        }
        return s.length();
    }

    public static void main(String[] args) {
        System.out.println(safeLength("abc"));
        System.out.println(safeLength(42));
    }
}

public class Main {
    static final class Point {
        final int x, y;
        Point(int x, int y) { this.x = x; this.y = y; }
        public boolean equals(Object o) {
            return o instanceof Point p && p.x == x && p.y == y;
        }
        public int hashCode() { return x * 31 + y; }
    }

    public static void main(String[] args) {
        System.out.println(new Point(1, 2).equals(new Point(1, 2)));
        System.out.println(new Point(1, 2).equals(new Point(3, 4)));
    }
}

public class Main {
    static String describe(Object obj) {
        if (obj instanceof Integer i) {
            return "int " + (i * 2);
        } else if (obj instanceof String s) {
            return "string of length " + s.length();
        } else {
            return "unknown";
        }
    }

    public static void main(String[] args) {
        System.out.println(describe(21));
        System.out.println(describe("hello"));
        System.out.println(describe(3.14));
    }
}

public class Main {
    public static void main(String[] args) {
        Object obj = null;
        if (obj instanceof String s) {
            System.out.println("matched: " + s);
        } else {
            System.out.println("null or not a String");
        }
    }
}

public class Main {
    static String format(Object o) {
        if (o instanceof Double d) return String.format("%.1f", d);
        if (o instanceof Integer i) return Integer.toString(i);
        if (o instanceof String s && !s.isBlank()) return s.trim();
        return "n/a";
    }

    public static void main(String[] args) {
        System.out.println(format(3.14159));
        System.out.println(format(99));
        System.out.println(format("  spaced  "));
        System.out.println(format(null));
    }
}