fix

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

@@ -0,0 +1,62 @@
+package org.Exceptions;
+
+import java.util.regex.Pattern;
+
+public class RuntimeExceptionDemo {
+    public static void main(String[] args) {
+
+        UserEntity user = new UserEntity("Ali", "Ahmadi", 1234567890L,
+                null, 989111111111L, null);
+
+        validateEmail(user);
+        calculatePayment(5000, 0);
+        convertUserAge("twenty");
+        completeRegistration(user);
+
+    }
+
+
+    //nullPointerException
+    //IllegalArgumentException
+    public static void validateEmail(UserEntity user) {
+
+        String email = user.getEmail();
+
+        String emailRegex = "^[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+$";
+
+        if (!Pattern.matches(emailRegex, email)) {
+            throw new IllegalArgumentException("Invalid email format");
+        }
+
+        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");
+    }
+
+}