// ❌ Wrong: Magic numbers
if (status == 1) { ... }

// ✅ Correct: Named constants
private static final int STATUS_ACTIVE = 1;
if (status == STATUS_ACTIVE) { ... }

// ❌ Wrong: Comparing wrapper types with ==
Integer a = 128;
Integer b = 128;
if (a == b) { ... }  // May fail!

// ✅ Correct: Use equals()
if (a.equals(b)) { ... }

// ❌ Wrong: Empty catch block
try {
    doSomething();
} catch (Exception e) {
    // Silent failure
}

// ✅ Correct: Handle or rethrow
try {
    doSomething();
} catch (Exception e) {
    logger.error("Failed to do something", e);
    throw new BusinessException("Operation failed", e);
}

// ❌ Wrong: Creating threads directly
new Thread(() -> doWork()).start();

// ✅ Correct: Use thread pool
ExecutorService executor = new ThreadPoolExecutor(
    corePoolSize, maxPoolSize, keepAliveTime,
    TimeUnit.SECONDS, new LinkedBlockingQueue<>(),
    new ThreadFactoryBuilder().setNameFormat("worker-%d").build()
);
executor.submit(() -> doWork());

// ✅ Correct: Parameterized query
String sql = "SELECT id, user_name, email FROM user WHERE id = ?";
PreparedStatement ps = conn.prepareStatement(sql);
ps.setLong(1, userId);

// ✅ Correct: MyBatis parameter binding
@Select("SELECT * FROM user WHERE user_name = #{userName}")
User selectByUserName(@Param("userName") String userName);

// ❌ Wrong: String concatenation (SQL injection risk!)
String sql = "SELECT * FROM user WHERE user_name = '" + userName + "'";

// ✅ Correct exception handling
public User getUserById(Long userId) {
    if (userId == null) {
        throw new IllegalArgumentException("userId cannot be null");
    }

    User user = userDao.selectById(userId);
    if (user == null) {
        throw new NotFoundException("User not found: " + userId);
    }

    return user;
}

// ✅ Correct logging with exception
try {
    processOrder(order);
} catch (Exception e) {
    logger.error("Failed to process order, orderId: {}", order.getId(), e);
    throw new BusinessException("订单处理失败", e);
}

// ✅ Correct: Thread pool with proper configuration
ThreadPoolExecutor executor = new ThreadPoolExecutor(
    10,  // corePoolSize
    20,  // maximumPoolSize
    60L, // keepAliveTime
    TimeUnit.SECONDS,
    new LinkedBlockingQueue<>(100),
    new ThreadFactoryBuilder().setNameFormat("order-processor-%d").build(),
    new ThreadPoolExecutor.CallerRunsPolicy()
);

// ✅ Correct: ThreadLocal cleanup
private static final ThreadLocal<User> USER_CONTEXT = new ThreadLocal<>();

public void processRequest() {
    try {
        USER_CONTEXT.set(getCurrentUser());
        // Process request
    } finally {
        USER_CONTEXT.remove();  // Critical: prevent memory leak
    }
}

// ✅ Correct: Input validation
public void createUser(UserCreateRequest request) {
    if (StringUtils.isBlank(request.getUserName())) {
        throw new ValidationException("用户名不能为空");
    }
    if (!ValidationUtils.isValidMobile(request.getMobile())) {
        throw new ValidationException("手机号格式不正确");
    }
    // Process...
}

// ✅ Correct: Sensitive data masking
logger.info("User login, mobile: {}", maskMobile(user.getMobile()));

@ExtendWith(MockitoExtension.class)
public class UserServiceTest {

    @Mock
    private UserDao userDao;

    @InjectMocks
    private UserService userService;

    @Test
    @DisplayName("根据ID获取用户 - 正常情况")
    public void testGetUserById_Success() {
        // Given
        Long userId = 1L;
        User mockUser = new User();
        mockUser.setId(userId);
        mockUser.setUserName("test");
        when(userDao.selectById(userId)).thenReturn(mockUser);

        // When
        User result = userService.getUserById(userId);

        // Then
        assertNotNull(result);
        assertEquals(userId, result.getId());
        verify(userDao, times(1)).selectById(userId);
    }

    @Test
    @DisplayName("根据ID获取用户 - 参数为null")
    public void testGetUserById_NullParameter() {
        assertThrows(IllegalArgumentException.class, () -> {
            userService.getUserById(null);
        });
    }
}