Implementation of WS-05 is completed

src/main/java/org/Exceptions/RuntimeExceptionDemo.java

@@ -8,20 +8,47 @@ public class RuntimeExceptionDemo {
         UserEntity user = new UserEntity("Ali", "Ahmadi", 1234567890L,
                 null, 989111111111L, null);
 
-        validateEmail(user);
-        calculatePayment(5000, 0);
-        convertUserAge("twenty");
-        completeRegistration(user);
+        // 1. Handle NullPointerException / IllegalArgumentException
+        try {
+            validateEmail(user);
+        } catch (NullPointerException e) {
+            System.err.println("Caught NullPointerException: Email string cannot be null.");
+        } catch (IllegalArgumentException e) {
+            System.err.println("Caught IllegalArgumentException: " + e.getMessage());
+        }
 
+        // 2. Handle ArithmeticException
+        try {
+            calculatePayment(5000, 0);
+        } catch (ArithmeticException e) {
+            System.err.println("Caught ArithmeticException: Cannot divide payment by zero installments.");
+        }
+
+        // 3. Handle NumberFormatException
+        try {
+            convertUserAge("twenty");
+        } catch (NumberFormatException e) {
+            System.err.println("Caught NumberFormatException: Could not parse invalid age string.");
+        }
+
+        // 4. Handle IllegalStateException
+        try {
+            completeRegistration(user);
+        } catch (IllegalStateException e) {
+            System.err.println("Caught IllegalStateException: " + e.getMessage());
+        }
+
+        System.out.println("\nRuntimeExceptionDemo executed completely and safely!");
     }
 
-
-    //nullPointerException
-    //IllegalArgumentException
     public static void validateEmail(UserEntity user) {
-
         String email = user.getEmail();
 
+        // Fix to prevent immediate NullPointerException before regex matching
+        if (email == null) {
+            throw new NullPointerException("Email cannot be null");
+        }
+
         String emailRegex = "^[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+$";
 
         if (!Pattern.matches(emailRegex, email)) {
@@ -31,32 +58,22 @@ public class RuntimeExceptionDemo {
         System.out.println("User email is valid");
     }
 
-    // ArithmeticException
     public static void calculatePayment(int totalAmount, int installmentCount) {
-
         int payment = totalAmount / installmentCount;
-
         System.out.println("Each installment : " + payment);
     }
 
-    // NumberFormatException
     public static void convertUserAge(String ageInput) {
-
         int age = Integer.parseInt(ageInput);
-
         System.out.println("User age: " + age);
     }
 
-//    IllegalStateException
     public static void completeRegistration(UserEntity user) {
-
         if (user.getDateOfBirth() == null) {
             throw new IllegalStateException(
                     "Registration cannot be completed. Date of birth is missing."
             );
         }
-
         System.out.println("Registration completed");
     }
-
 }