feat: Add CalculateDiscount class with variable argument discount calculator

WHAT the code does:
- Defines a `CalculateDiscount` class with method `calculateTotalWithDiscount(double... prices)`:
  - Accepts a variable number of price values.
  - Sums all the prices.
  - Applies discounts based on total:
    - `< 500` → 10% discount.
    - `500–1000` → 5% discount.
    - `> 1000` → no discount.
  - Returns final discounted total.
- `main()` tests the method with three examples:
  1. `(100, 150, 200)` → total `450`, 10% discount → `405.0`.
  2. `(300, 250)` → total `550`, 5% discount → `522.5`.
  3. `(600, 500)` → total `1100`, no discount → `1100.0`.

WHY this matters:
- Demonstrates **varargs (variable arguments)** in methods.
- Combines iteration, conditional logic, and return values.
- Simulates a real-world use case: applying discounts based on order total.

HOW it works:
1. Enhanced `for` loop calculates total sum.
2. Conditional logic (`if / else if / else`) applies correct discount tier.
3. Prints messages to explain discount applied.
4. Final discounted total is printed in each test case.

Tips & gotchas:
- Conditions are mutually exclusive, ensuring only one discount applies.
- Precision issues may arise with floating-point values; use `BigDecimal` for money in real applications.
- Current implementation applies discount once on total — not per item.
- Varargs allows flexibility: `calculateTotalWithDiscount()` can take any number of price inputs.

Use-cases:
- Educational demo of **varargs + conditional logic**.
- Useful for e-commerce or billing simulations.
- Good practice for method design with real-world scenarios.
- Can be extended with multiple discount strategies, loyalty points, or tax calculation.

Short key: class-calculatediscount-varargs-discount.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section10Methods/src/CalculateDiscount.java

@@ -1,36 +1,41 @@
-public class CalculateDiscount{
-    // Method to calculate the total after applying a discount
-    double calculateTotalWithDiscount(double... prices) {
-        // Calculate the sum of all prices
+public class CalculateDiscount {
+    double calculateTotalWithDiscount(double... prices)
+    // Method to calculate the total after applying a discount.
+    {
         double sum = 0;
+
+        // Calculate the sum of all prices.
         for (double price : prices) {
             sum += price;
         }
 
-        // Apply discounts based on the sum
-        if (sum < 500) {
+        if (sum < 500)
+        // Apply discounts based on the sum.
+        {
             System.out.println("Applying 10% discount (Total is less than 500).");
-            return sum * 0.9; // 10% discount
-        } else if (sum >= 500 && sum <= 1000) {
+            return sum * 0.9; // 10% discount.
+        }
+        else if (sum >= 500 && sum <= 1000)
+        {
             System.out.println("Applying 5% discount (Total is between 500 and 1000).");
             return sum * 0.95; // 5% discount
-        } else {
+        }
+        else
+        {
             System.out.println("No discount applied (Total is greater than 1000).");
             return sum; // No discount for totals above 1000
         }
     }
-
     public static void main(String[] args) {
         CalculateDiscount calculator = new CalculateDiscount();
 
-        // Example usage
-        double total1 = calculator.calculateTotalWithDiscount(100, 150, 200); // Total = 450
-        System.out.println("Total after discount: " + total1); // Should print 405.0
+        double total1 = calculator.calculateTotalWithDiscount(100, 150, 200);
+        System.out.println("Total after discount: " + total1);
 
-        double total2 = calculator.calculateTotalWithDiscount(300, 250); // Total = 550
-        System.out.println("Total after discount: " + total2); // Should print 522.5
+        double total2 = calculator.calculateTotalWithDiscount(300, 250);
+        System.out.println("Total after discount: " + total2);
 
-        double total3 = calculator.calculateTotalWithDiscount(600, 500); // Total = 1100
-        System.out.println("Total after discount: " + total3); // Should print 1100.0
+        double total3 = calculator.calculateTotalWithDiscount(600, 500);
+        System.out.println("Total after discount: " + total3);
     }
 }