الدوال (Methods)

public class Main {
    static double withVat(double price) {
        return price + price * 0.16;
    }

    public static void main(String[] args) {
        System.out.println(withVat(100));   // 116.0
        System.out.println(withVat(250));   // 290.0
    }
}

static int add(int a, int b) {
    return a + b;
}

public class Main {
    static void printReceipt(String item, double price) {
        System.out.println("المنتج: " + item);
        System.out.printf("السعر: %.2f دينار%n", price);
        System.out.println("-----");
    }

    public static void main(String[] args) {
        printReceipt("كتاب", 12.5);
        printReceipt("قلم", 0.75);
    }
}

public class Main {
    static String classify(int age) {
        if (age < 0) {
            return "عمر غير صالح";
        }
        if (age < 18) {
            return "قاصر";
        }
        return "بالغ";
    }

    public static void main(String[] args) {
        System.out.println(classify(-3));
        System.out.println(classify(12));
        System.out.println(classify(30));
    }
}

public class Main {
    static void addBonus(int salary) {
        salary += 100;
        System.out.println("داخل الدالة: " + salary);   // 1100
    }

    static void doubleAll(int[] values) {
        for (int i = 0; i < values.length; i++) {
            values[i] *= 2;
        }
    }

    public static void main(String[] args) {
        int salary = 1000;
        addBonus(salary);
        System.out.println("بعدها: " + salary);          // 1000 لم يتغيّر

        int[] nums = {1, 2, 3};
        doubleAll(nums);
        System.out.println(java.util.Arrays.toString(nums));   // [2, 4, 6] تغيّر!
    }
}

public class Main {
    static int square(int n) {
        int result = n * n;    // result محلي لهذه الدالة
        return result;
    }

    public static void main(String[] args) {
        System.out.println(square(7));
        // System.out.println(result);  ❌ cannot find symbol
    }
}

public class Main {
    static int area(int side) {
        return side * side;                 // مربّع
    }

    static int area(int width, int height) {
        return width * height;              // مستطيل
    }

    static double area(double radius) {
        return Math.PI * radius * radius;   // دائرة
    }

    public static void main(String[] args) {
        System.out.println(area(4));        // 16
        System.out.println(area(4, 5));     // 20
        System.out.println(area(1.0));      // 3.141592653589793
    }
}

public class Main {
    static int sum(int... numbers) {
        int total = 0;
        for (int n : numbers) {
            total += n;
        }
        return total;
    }

    public static void main(String[] args) {
        System.out.println(sum());             // 0
        System.out.println(sum(5));            // 5
        System.out.println(sum(1, 2, 3, 4));   // 10
    }
}