Implementing Code

Workflows

• Security Check: Injection flaws, auth issues, sensitive data exposure

• Performance Check: N+1 queries, memory leaks, inefficient algorithms

• Readability Check: SOLID principles, naming conventions, comments

• Testing Check: Edge cases, error paths, happy paths

Feedback Loops

• Implement feature or fix

• Run local tests (unit/integration)

• Run linter/formatter

• If failure, fix and repeat

Reference Implementation

SOLID Compliant Class (Java + Spring Boot)

// Abstraction (Interface Segregation) public interface Logger { void log(String message); }

public interface UserRepository extends JpaRepository<User, Long> { boolean existsByEmail(String email); }

// Domain Entity @Entity @Data @Builder @NoArgsConstructor @AllArgsConstructor public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;

@Email(message = "Invalid email format")
@NotBlank(message = "Email is required")
private String email;

@Builder.Default
private Instant createdAt = Instant.now();

}

// Implementation (Single Responsibility) @Service @Transactional public class UserService { private final UserRepository userRepository; private final Logger logger;

public UserService(UserRepository userRepository, Logger logger) {
    this.userRepository = userRepository;
    this.logger = logger;
}

public User registerUser(String email) {
    // Validation
    if (!email.contains("@")) {
        throw new IllegalArgumentException("Invalid email format");
    }

    if (userRepository.existsByEmail(email)) {
        throw new DuplicateEmailException("Email already exists");
    }

    // Business logic
    User user = User.builder()
        .email(email)
        .build();

    User saved = userRepository.save(user);
    logger.log("User registered: " + saved.getId());

    return saved;
}

}

Code Review Checklist

• No hardcoded secrets or credentials

• Input validation on all external data

• Proper error handling with meaningful messages

• No N+1 query patterns

• Functions follow single responsibility principle

• Dependencies injected, not instantiated inline

• Tests cover happy path and edge cases