Java – Best Practices

• Prefer immutability — use final fields wherever possible
• Use Optional<T> for nullable return values — never return null from a public API
• Use streams and lambdas for collections — avoid nesting more than 2 levels
• Always override hashCode() when you override equals()
• Close resources in try-with-resources blocks
• Always add @Override on overridden methods
• Use @Transactional at the service layer, not the controller layer

Optional Example

// Correct
public Optional<User> findUser(Long id) {
    return userRepository.findById(id);
}

// Incorrect
public User findUser(Long id) {
    return userRepository.findById(id).orElse(null);
}

Try-With-Resources Example

// Correct
try (Connection conn = dataSource.getConnection()) {
    // use conn
}

// Incorrect
Connection conn = dataSource.getConnection();
// use conn — never closed if exception thrown