Separation of Concerns is a design principle that divides a system into distinct sections, each addressing a specific concern or responsibility. This reduces complexity and improves maintainability.
Benefits:

• Modularity: Each component has a single, well-defined purpose
• Maintainability: Changes to one concern don't affect others
• Reusability: Components can be reused across different contexts
• Testability: Each concern can be tested independently
  Example:

// Poor separation
class UserController {
    public void createUser(UserDto user) {
        // Validation logic
        if (user.email == null) throw new Exception();
        // Business logic
        User newUser = new User(user.name, user.email);
        // Data access logic
        database.save(newUser);
        // Notification logic
        emailService.sendWelcome(user.email);
    }
}
// Good separation
class UserController {
    public void createUser(UserDto user) {
        validator.validate(user);
        User newUser = userService.createUser(user);
        notificationService.sendWelcome(newUser);
    }
}