Java Patterns

Idiomatic Java/Spring patterns for Java 17+.

Records

public record User(String name, String email) {}

Optional

Optional.ofNullable(user)
    .map(User::getEmail)
    .orElse("default@example.com");

Streams

List<String> names = users.stream()
    .filter(u -> u.isActive())
    .map(User::getName)
    .collect(Collectors.toList());

Spring Dependency Injection

@Service
public class UserService {
    private final UserRepository repo;

    public UserService(UserRepository repo) {
        this.repo = repo;
    }
}

JUnit 5

@Test
void shouldReturnUser() {
    User user = service.findById(1L);
    assertThat(user.getName()).isEqualTo("test");
}

@ParameterizedTest
@ValueSource(strings = {"a", "b", "c"})
void shouldValidate(String input) {
    assertTrue(validator.isValid(input));
}