![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 10 List read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List list = new ArrayList(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileName), "UTF-8")); String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = df.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } } catch (ParseException e) { throw new RuntimeException("failed to parse date", e); } catch (IOException e) { throw new RuntimeException("failed to read file: " + fileName, e); } finally { try { if (reader != null) { reader.close(); } } catch (IOException e) { // ignore } } return list; } CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-10-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 2/3 12 String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = df.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx);
} CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-12-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 55 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = df.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx);
} CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-55-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 56 List<Transaction> read(String fileName) { // SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName))) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx);
} CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-56-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 57 List<Transaction> read(String fileName) { // SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName))) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx);
} UTF-8 Charset
ISO 8601
CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-57-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 66 List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName))) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx);
} } catch (ParseException | IOException e) { throw new RuntimeException("failed to parse date or read file”, e); } return list; CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-66-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 67 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); } CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-67-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 68 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); }
Stream
List CSV
String Transaction](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-68-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 69 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); } Lambda CSV](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-69-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 90 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); }
String Transaction List](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-90-2048.jpg)
![Copyright © Acroquest Technology Co., Ltd. All rights reserved. #ccc_g3 JShell 102 // jshell> List<Integer> intList = List.of(1, 2, 3); intList ==> [1, 2, 3] jshell> List<String> strList = List.of("aaa,", "bbb", “ccc"); strList ==> [aaa,, bbb, ccc] jshell> intList.add(4); | java.lang.UnsupportedOperationException thrown: | at ImmutableCollections.uoe (ImmutableCollections.java:71) ( )](https://image.slidesharecdn.com/cccg3-java9java-171118085122/75/Java9-Java-102-2048.jpg)
Uploaded byTakuya Okada
Java9を迎えた今こそ！Java本格(再)入門
The document discusses Java programming and transactions. It describes reading transaction data from a CSV file, parsing the data into Transaction objects, and summarizing the transaction amounts. It covers improvements such as using generics, try-with-resources for file handling, LocalDate instead of Date, and various Java features between versions.
Java9を迎えた今こそ！Java本格(再)入門
- 1.
- 2. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2 Java Chapter 7 Chapter 8 Chapter 9 Chapter 12 Acroquest Technology - 2017 3 2Twitter: @omochiya -
- 3. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 3
- 4. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 4
- 5. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1.Introduction 2.Java 1.4 -> 5.0 3.Java 5.0 -> 7 4.Java 7 -> 8 5.Java 8 -> 9 6.Java 9 -> Future 5
- 6. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 6
- 7. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 7
- 8. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 8 CSV File 2017-09-25,100,123456,Acroquest, 2017-10-02,100,-28980, , 2017-10-03,100,-17712, , 2017-10-20,100,3000000,gihyo, 2017-10-25,100,200000,Acroquest, , , , , etc
- 9. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 9
- 10. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 10 List read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List list = new ArrayList(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileName), "UTF-8")); String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = df.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } } catch (ParseException e) { throw new RuntimeException("failed to parse date", e); } catch (IOException e) { throw new RuntimeException("failed to read file: " + fileName, e); } finally { try { if (reader != null) { reader.close(); } } catch (IOException e) { // ignore } } return list; } CSV
- 11. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 11 List read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List list = new ArrayList(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader( new FileInputStream(fileName), "UTF-8")); CSV
- 12. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2/3 12 String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = df.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } CSV
- 13. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 3/3 13 } catch (ParseException e) { throw new RuntimeException("failed to parse date", e); } catch (IOException e) { throw new RuntimeException("failed to read file: " + fileName, e); } finally { try { if (reader != null) { reader.close(); } } catch (IOException e) { // ignore } } return list; } finally close CSV
- 14. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction 14 class Transaction { Date date; String accountId; Integer amount; String name; String note; public Transaction() { } public Transaction(Date date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } public String toString() { return date + " " + accountId + " " + amount + " " + name + " " + note; } } CSV
- 15. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction 1/2 15 class Transaction { Date date; String accountId; Integer amount; String name; String note; public Transaction() { } CSV
- 16. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction 2/2 16 public Transaction(Date date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } public String toString() { return date + " " + accountId + " " + amount + " " + name + " " + note; } } CSV
- 17. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 17 List list = read(fileName); int sum = 0; for (int i = 0; i < list.size(); i++) { Transaction tx = (Transaction) list.get(i); sum += tx.amount; } System.out.println(sum); CSV
- 18. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 6 18 List list = read(fileName); for (int i = 0; i < list.size(); i++) { Transaction tx = (Transaction) list.get(i); Calendar cal = Calendar.getInstance(); cal.setTime(tx.date); if (cal.get(Calendar.MONTH) == 5) { System.out.println(tx); } } 0 CSV
- 19. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 19
- 20. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 20
- 21. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 21
- 22. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 22 List read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List list = new ArrayList(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader( new FileInputStream(fileName), "UTF-8")); CSV
- 23. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 23 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<Transaction>(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader( new FileInputStream(fileName), "UTF-8")); CSV
- 24. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 24 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<Transaction>(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader( new FileInputStream(fileName), "UTF-8")); Generics → → CSV
- 25. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 25 List list = read(fileName); int sum = 0; for (int i = 0; i < list.size(); i++) { Transaction tx = (Transaction) list.get(i); sum += tx.amount; } System.out.println(sum); CSV
- 26. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 26 List<Transaction> list = read(fileName); int sum = 0; for (Transaction tx : list) { sum += tx.amount; } System.out.println(sum); CSV
- 27. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 27 List<Transaction> list = read(fileName); int sum = 0; for (Transaction tx : list) { sum += tx.amount; } System.out.println(sum); CSV for →
- 28. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 28
- 29. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction 2/2 29 public Transaction(Date date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } public String toString() { return date + " " + accountId + " " + amount + " " + name + " " + note; } } CSV
- 30. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction 2/2 30 public Transaction(Date date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } @Override public String toString() { return date + " " + accountId + " " + amount + " " + name + " " + note; } } CSV
- 31. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction 2/2 31 public Transaction(Date date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } @Override public String toString() { return date + " " + accountId + " " + amount + " " + name + " " + note; } } → Override CSV
- 32. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 32
- 33. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 33
- 34. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 34
- 35. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 35
- 36. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 36 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<Transaction>(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader( new FileInputStream(fileName), "UTF-8")); CSV
- 37. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 37 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { CSV
- 38. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 38 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { CSV
- 39. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 39 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { try-with-resoureces try ( ) close → → CSV
- 40. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 40
- 41. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 41 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { Files nio2 CSV
- 42. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1/3 42 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { String Charset StandardCharsets → CSV
- 43. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 3/3 43 } catch (ParseException e) { throw new RuntimeException("failed to parse date", e); } catch (IOException e) { throw new RuntimeException("failed to read file: " + fileName, e); } finally { try { if (reader != null) { reader.close(); } } catch (IOException e) { // ignore } } return list; } CSV
- 44. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 3/3 44 } catch (ParseException | IOException e) { throw new RuntimeException("failed to parse date or read file”, e); } return list; } catch CSV
- 45. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 45
- 46. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 46
- 47. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 47
- 48. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 48
- 49. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 49
- 50. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 50
- 51. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction toString 51 class Transaction { Date date; String accountId; Integer amount; String name; String note; public Transaction() { } public Transaction(Date date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } CSV
- 52. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction toString 52 class Transaction { LocalDate date; String accountId; Integer amount; String name; String note; public Transaction() { } public Transaction(LocalDate date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } CSV
- 53. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 Transaction toString 53 class Transaction { LocalDate date; String accountId; Integer amount; String name; String note; public Transaction() { } public Transaction(LocalDate date, String accountId, Integer amount, String name, String note) { this.date = date; this.accountId = accountId; this.amount = amount; this.name = name; this.note = note; } Date and Time API →LocalDate LocalDateTime LocalTime OffsetDateTime ZonedDateTime CSV
- 54. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 54
- 55. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 55 List<Transaction> read(String fileName) { SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName), StandardCharsets.UTF_8)) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = df.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } CSV
- 56. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 56 List<Transaction> read(String fileName) { // SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName))) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } CSV
- 57. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 57 List<Transaction> read(String fileName) { // SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd"); List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName))) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } UTF-8 Charset ISO 8601 CSV
- 58. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 58
- 59. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 6 59 List<Transaction> list = read(fileName); for (Transaction tx : list) { Calendar cal = Calendar.getInstance(); cal.setTime(tx.date); if (cal.get(Calendar.MONTH) == 5) { System.out.println(tx); } } CSV
- 60. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 6 60 List<Transaction> list = read(fileName); for (Transaction tx : list) { if (tx.date.getMonth() == Month.JUNE) { System.out.println(tx); } } CSV
- 61. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 - 6 61 List<Transaction> list = read(fileName); for (Transaction tx : list) { if (tx.date.getMonth() == Month.JUNE) { System.out.println(tx); } } enum enum → 0 CSV
- 62. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 62
- 63. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 63
- 64. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 64
- 65. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 65
- 66. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 66 List<Transaction> list = new ArrayList<>(); try (BufferedReader reader = Files.newBufferedReader(Paths.get(fileName))) { String line; while ((line = reader.readLine()) != null) { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; list.add(tx); } } catch (ParseException | IOException e) { throw new RuntimeException("failed to parse date or read file”, e); } return list; CSV
- 67. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 67 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); } CSV
- 68. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 68 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); } Stream List CSV String Transaction
- 69. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 69 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); } Lambda CSV
- 70. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1 70 // List<Transaction> list = read(fileName); // for (Transaction tx : list) { System.out.println(tx); } // int sum = 0; for (Transaction tx : list) { sum += tx.amount; } System.out.println(sum); CSV
- 71. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1 71 // read(fileName).stream() .forEach(System.out::println); // int sum = read(fileName).stream() .mapToInt(tx -> tx.amount) .sum(); System.out.println(sum); CSV
- 72. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1 72 // read(fileName).stream() .forEach(System.out::println); // int sum = read(fileName).stream() .mapToInt(tx -> tx.amount) .sum(); System.out.println(sum); int CSV
- 73. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1 73 // read(fileName).stream() .forEach(System.out::println); // int sum = read(fileName).stream() .mapToInt(tx -> tx.amount) .sum(); System.out.println(sum); Lambda CSV
- 74. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2 74 // 6 for (Transaction tx : list) { if (tx.date.getMonth() == Month.JUNE) { System.out.println(tx); } } CSV
- 75. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2 75 // 6 read(fileName).stream() .filter(tx -> tx.date.getMonth() == Month.JUNE) .forEach(System.out::println); CSV
- 76. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2 76 // 6 read(fileName).stream() .filter(tx -> tx.date.getMonth() == Month.JUNE) .forEach(System.out::println); 6 filter CSV
- 77. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2 77 // 6 read(fileName).stream() .filter(tx -> tx.date.getMonth() == Month.JUNE) .forEach(System.out::println); Lambda
- 78. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 78
- 79. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 79
- 80. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 80
- 81. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 81
- 82. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 82
- 83. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 83
- 84. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 84
- 85. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 85
- 86. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 86
- 87. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 87
- 88. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 88
- 89. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 89
- 90. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 90 try (Stream<String> stream = Files.lines(Paths.get(fileName))) { return stream .map(line -> { String[] s = line.split(","); Transaction tx = new Transaction(); tx.date = LocalDate.parse(s[0]); tx.accountId = s[1]; tx.amount = Integer.valueOf(s[2]); tx.name = s[3]; tx.note = s[4]; return tx; }) .collect(Collectors.toList()); } catch (ParseException | IOException e) { throw new UncheckedIOException("failed to read file", e); } String Transaction List
- 91. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 1 91 // read(fileName).stream() .forEach(System.out::println); // int sum = read(fileName).stream() .mapToInt(tx -> tx.amount) .sum(); System.out.println(sum); int
- 92. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 2 92 // 6 read(fileName).stream() .filter(tx -> tx.date.getMonth() == Month.JUNE) .forEach(System.out::println); 6 filter
- 93. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 93
- 94. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 94
- 95. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 95
- 96. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 96
- 97. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 97
- 98. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 98
- 99. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 99
- 100. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 100
- 101. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 101
- 102. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 JShell 102 // jshell> List<Integer> intList = List.of(1, 2, 3); intList ==> [1, 2, 3] jshell> List<String> strList = List.of("aaa,", "bbb", “ccc"); strList ==> [aaa,, bbb, ccc] jshell> intList.add(4); | java.lang.UnsupportedOperationException thrown: | at ImmutableCollections.uoe (ImmutableCollections.java:71) ( )
- 103. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 JShell 103 // jshell> Map<Integer, String> map = Map.of(1, "aaa", 2, "bbb", 3, “ccc"); map ==> {1=aaa, 2=bbb, 3=ccc} jshell> map.put(4, "ddd"); | java.lang.UnsupportedOperationException thrown: | at ImmutableCollections.uoe (ImmutableCollections.java:71) ( )
- 104. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 104
- 105. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 105
- 106. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 106 // var str = “Hello”; final var MAXIMUM = 100L; // NG var array = {1, 2, 3}; var list = new ArrayList<>();
- 107. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 107
- 108. Copyright © AcroquestTechnology Co., Ltd. All rights reserved. #ccc_g3 108