static void optionalTest() {
// 不要这样,这与!=null没什么区别
Optional<String> stringOptional = Optional.of("alibaba");
if (stringOptional.isPresent()) {
System.out.println(stringOptional.get().length());
}
Optional<String> optionalValue = Optional.of("alibaba");
// 下面是推荐的常用操作
optionalValue.ifPresent(s -> System.out.println(s + " contains red"));
// 增加到集合汇总
List<String> results = Lists.newArrayList();
optionalValue.ifPresent(results::add);
// 增加到集合中，并返回操作结果
Optional<Boolean> added = optionalValue.map(results::add);
// 无值的optional
Optional<String> optionalString = Optional.empty();
// 不存在值，返回“No word”
String result = optionalValue.orElse("No word");
// 没值，计算一个默认值
result = optionalString.orElseGet(() -> System.getProperty("user.dir"));
// 无值，抛一个异常
try {
result = optionalString.orElseThrow(NoSuchElementException::new);
} catch (Throwable t) {
t.getCause();
}
}
@Test
public void _07_옵션_다루기() {
final Optional<String> optional = words.stream().filter(w -> w.contains("red")).findFirst();
try {
optional.ifPresent(
v -> {
throw new RuntimeException();
});
assert false; // 이 행은 실행되면 안됨.
} catch (RuntimeException e) {
}
// 비어있는 경우는 실행되지 않음.
Optional.empty()
.ifPresent(
v -> {
throw new RuntimeException();
});
Set<String> results = new HashSet<>();
optional.ifPresent(results::add);
assertThat(results.contains("tired"), is(true));
// 실행 결과를 받고 싶은 경우에는 map 사용.
results = new HashSet<>();
Optional<Boolean> added = optional.map(results::add);
assertThat(added, is(Optional.of(Boolean.TRUE)));
// 대상이 빈경우에는 empty Optional 반환
Optional<Boolean> a = Optional.empty().map(v -> true);
assertThat(a.isPresent(), is(false));
Optional<String> emptyOptional = Optional.empty();
// orElse로 기본값 지정 가능
String result = emptyOptional.orElse("기본값");
assertThat(result, is("기본값"));
// 기본값 생성하는 코드 호출 가능
result = emptyOptional.orElseGet(() -> System.getProperty("user.dir"));
assertThat(result, is(System.getProperty("user.dir")));
// 값이 없는 경우 예외 던지기
try {
emptyOptional.orElseThrow(NoSuchElementException::new);
assert false;
} catch (NoSuchElementException e) {
}
}
/**
* @param directoryWithUnpackedFiles Directory with unpacked files (should include BBIs and DBF)
* @return Map of BBI files names to their corresponding verifications
* @throws SQLException
* @throws ClassNotFoundException
* @throws FileNotFoundException
* @implNote Uses sqlite to open DBF
*/
private Map<String, Map<String, String>> getVerificationMapFromUnpackedFiles(
File directoryWithUnpackedFiles)
throws SQLException, ClassNotFoundException, FileNotFoundException {
Map<String, Map<String, String>> bbiFilesToVerification = new LinkedHashMap<>();
Map<String, String> verificationMap;
Optional<File> foundDBFile =
FileUtils.listFiles(directoryWithUnpackedFiles, dbfExtensions, true).stream().findFirst();
File dbFile = foundDBFile.orElseThrow(() -> new FileNotFoundException("DBF not found"));
Class.forName("org.sqlite.JDBC");
try (Connection connection = DriverManager.getConnection("jdbc:sqlite:" + dbFile)) {
Statement statement = connection.createStatement();
ResultSet rs = statement.executeQuery("SELECT * FROM Results");
while (rs.next()) {
verificationMap = new LinkedHashMap<>();
verificationMap.put(Constants.VERIFICATION_ID, rs.getString("Id_pc"));
verificationMap.put(Constants.PROVIDER, rs.getString("Customer"));
verificationMap.put(Constants.DATE, rs.getString("Date"));
verificationMap.put(Constants.COUNTER_NUMBER, rs.getString("CounterNumber"));
verificationMap.put(Constants.COUNTER_SIZE_AND_SYMBOL, rs.getString("Type"));
verificationMap.put(Constants.YEAR, rs.getString("Year"));
verificationMap.put(Constants.STAMP, rs.getString("Account"));
verificationMap.put(Constants.LAST_NAME, rs.getString("Surname"));
verificationMap.put(Constants.FIRST_NAME, rs.getString("Name"));
verificationMap.put(Constants.MIDDLE_NAME, rs.getString("Middlename"));
verificationMap.put(Constants.PHONE_NUMBER, rs.getString("TelNumber"));
verificationMap.put(Constants.REGION, rs.getString("District"));
verificationMap.put(Constants.CITY, rs.getString("City"));
verificationMap.put(Constants.STREET, rs.getString("Street"));
verificationMap.put(Constants.BUILDING, rs.getString("Building"));
verificationMap.put(Constants.FLAT, rs.getString("Apartment"));
bbiFilesToVerification.put(rs.getString("FileNumber"), verificationMap);
}
}
return bbiFilesToVerification;
}
