Evolution of Java

A recap of the evolution of Java starting with the JDK5 and finishing with the new api of date/time and lamdbas.

The code is in github (https://github.com/nhpatt/evolution_of_java), showing how to do it in Java 5 and 8.

Transcript

1. Evolution Of Java From Java 5 to 8
2. I want CODE Here it is
3. State of the union • Currently in Java 7 o Luce has some projects working with Java 7 (ipamms, aernova…), the rest of them are Java 6. • Java 8 expected in spring 2014.
4. Java 5 • September 2004 (old!, almost 9 years) o Annotations o Generics List values = new ArrayList(); values.add("value 1"); values.add(3); String value=(String) values.get(0); String value2=(String) values.get(1); List<String> values = new ArrayList<String>(); values.add("value 1"); values.add(new Integer(3)); String value= values.get(0); Integer value1= values.get(1); OLDER JAVA JAVA 5 Compiled, but exception at runtime!! compilation error
5. Java 5 o Autoboxing/unboxing List<Integer> values = new ArrayList<Integer>(); values.add(3); int value=values.get(0); JAVA 5 value=primitive; BOXING primitive=value ; UNBOXING Automatic operation With generics the type can’t be a primitive, but is not a problem Integer value; int primitive; o Enumerations:  Special data type that enables for a variable to be a set of predefined constants
6. public enum State{ INCOMPLETE("Incompl","YELLOW"),CORRECT("Correct","GREEN"), INCORRECT("Incorrect","RED"); private String name; private String color; private State(final String name, final String color) { this.name = name; this.color=color; } public String getName() { return name; } public String getColor() { return color; } public static List<State> getStateValues() { return Arrays.asList(INCOMPLETE, CORRECT,INCORRECT); } } private State state=State.CORRECT; Assert.assertEquals("GREEN", state.getColor());
7. Java 5 String result = ""; for (int i = 0; i < values.size(); i++) { result += values.get(i) + "-"; } String result = ""; for (final String value : values) { result += value + "-"; } OLDER JAVA JAVA 5 o Foreach o Static imports double r = Math.cos(PI * theta); OLDER JAVA JAVA 5 double r = Math.cos(Math.PI * theta);
8. sumTwo(2, 2)); //two numbers sumThree(2, 2, 2)); //three numbers public int sumTwo(final int a, final int b) { return a + b; } public int sumThree(final int a, final int b, final int c) { return a + b + c; } sum(2, 2)); //two numbers sum(2, 2, 2)); //three numbers public int sum(final int... numbers) { int total = 0; for (final int number : numbers) { total += number; } return total; } OLDER JAVA JAVA 5 o Varargs Java 5
9. Java 6 • December 2006 o No language changes o Scripting support o Improvements in Swing o JDBC 4.0 support o ...
10. Java 7 • July 2011 (ok, now we are talking) o JVM support for dynamic languages o Binary integer literals/underscores o Varargs simplified int million = 1_000_000 int telephone = 983_71_25_03 int num = 0b101
11. public String getColor (final String state) { if (("correct".equals(state)) { return "green"; } else if("incorrect".equals(state)) { return "red"; } else if ("incomplete".equals(state)){ return "yellow"; } else { return "white"; } } public String getColor(final String state) { switch (state) { case "correct": return "green"; case "incorrect": return "red"; case "incomplete": return "yellow"; default: return "white"; } } OLDER JAVA STRINGS IN SWITCH - JAVA 7 o Strings in switch
12. public void newFile() { FileOutputStream fos = null; DataOutputStream dos = null; try { fos = new FileOutputStream("path.txt"); dos = new DataOutputStream(fos); dos.writeBytes("prueba"); } catch (final IOException e) { e.printStackTrace(); } finally { // close resources try { dos.close(); fos.close(); } catch (final IOException e) { e.printStackTrace(); } } } public boolean newFile() { try (FileOutputStream fos = new FileOutputStream("path.txt"); DataOutputStream dos = new DataOutputStream(fos);) { dos.writeBytes("prueba"); dos.writeBytes("\r\n"); } catch (final IOException e) { e.printStackTrace(); } } OLDER JAVA TRY WITH RESOURCES (ARM) - JAVA 7 o Automatic resource management in try- catch
13. private Map<Integer, List<String>> createMapOfValues(final int... keys) { final Map<Integer, List<String>> map = new HashMap<Integer, List<String>>(); for (final int key : keys) { map.put(key, getListOfValues()); } return map; } private Map<Integer, List<String>> createMapOfValues(final int... keys) { final Map<Integer, List<String>> map = new HashMap<>(); for (final int key : keys) { map.put(key, getListOfValues()); } return map; } OLDER JAVA DIAMOND OPERATOR - JAVA 7 private ArrayList<String> getListOfValues() { return new ArrayList<String>(Arrays.asList("value1", "value2")); } private ArrayList<String> getListOfValues() { return new ArrayList<>(Arrays.asList("value1", "value2")); } o Diamond Operator
14. public double divide() { double result = 0d; try { int a = Integer.parseInt(num1); int b = Integer.parseInt(num2); result = a / b; } catch (NumberFormatException ex1) { System.out.println("invalid number"); } catch (ArithmeticException ex2) { System.out.println("zero"); } catch (Exception e) { e.printStackTrace(); } return result; } public double divide(){ double result = 0d; try { int a = Integer.parseInt(num1); int b = Integer.parseInt(num2); result = a / b; } catch (NumberFormatException|ArithmeticException ex){ System.out.println("invalid number or zero"); } catch (Exception e) { e.printStackTrace(); } return result; } OLDER JAVA MULTI CATCH - JAVA 7 o Catch multiple exceptions
15. Java 7 • New File I/O Path path = Paths.get("C:\\Users/Pili/Documents/f.txt"); path.getFileName(); -> "f.txt" path.getName(0); -> "Users" path.getNameCount(); -> 4 path.subpath(0, 2); -> "Users/Pili" path.getParent(); -> "C:\\Users/Pili/Documents" path.getRoot(); -> "C:\\" path.startsWith("C:\\Users"); -> true for (final Path name : path) { System.out.println(name); } java.io.File o Solves problems o New methods to manipulate files java.nio.file.Path
16. final File file = new File(path); file.createNewFile(); final Path file= Paths.get(path); Files.createFile(file); new file new file BufferedWriter bw = null; try { bw =new BufferedWriter(new FileWriter(file)); bw.write("Older Java: This is first line"); bw.newLine(); bw.write("Older Java: This is second line"); } catch (final IOException e) { e.printStackTrace(); } finally { try { bw.close(); } catch (final IOException ex) { System.out.println("Error"); } } try (BufferedWriter writer = Files.newBufferedWriter(file,Charset.defaultCharset()) ) { writer.append("Java 7: This is first line"); writer.newLine(); writer.append("Java 7: This is second line"); } catch (final IOException exception) { System.out.println("Error"); } write file write file
17. BufferedReader br = null; try { br = new BufferedReader(new FileReader(file)); String content; while ((content = br.readLine()) != null) { System.out.println(content); } } catch (final IOException e) { e.printStackTrace(); } finally { try{ br.close(); } catch (final IOException ex) { System.out.println("Error"); } } try (BufferedReader reader = Files.newBufferedReader (file, Charset.defaultCharset())) { String content= ""; while ((content = reader.readLine()) != null) { System.out.println(content); } } catch (final IOException exception) { System.out.println("Error"); } read file readfile file.delete(); Files.delete(file); delete file delete file
18. Java 8 • Spring 2014? o PermGen space disappears, new Metaspace  OutOfMemory errors disappear? -> not so fast o New methods in Collections (almost all lambda- related) o Small changes everywhere (concurrency, generics, String, File, Math)
19. Java 8 • Interfaces with static and default methods o ¿WTF? o Let’s look at Eclipse...
20. Java 8 public interface CalculatorInterfacePreJava8 { Integer add(Integer x, Integer y); // WTF do u think you are doing? // static Integer convert(Integer x); } public interface CalculatorInterfaceJava8 { default Integer add(Integer x, Integer y) { return x + y; } static Integer convert(Integer x) { return x * MAGIC_CONSTANT; } } OLDER JAVA JAVA 8
21. Java 8 • new Date and Time API (joda inspired) o Current was based on currentTimeMillis, Date and Calendar. o New one is based on continuous time and human time. o Inmutable.
22. Java 8 //Date oldDate = new Date(1984, 7, 8); oldDate = Calendar.getInstance(); oldDate.set(1984, 7, 8); date = LocalDate.of(1984, Month.AUGUST, 8); dateTime = LocalDateTime.of(1984, Month.AUGUST, 8, 13, 0); OLDER JAVA JAVA 8
23. Java 8 oldDate.set(Calendar.DAY_OF_MONTH, oldDate.get(Calendar.DAY_OF_MONT H) - 2); LocalDate sixOfAugust = date.minusDays(2); OLDER JAVA JAVA 8
24. Java 8 • Easier to add hours/days/… (plusDaysTest) • Easier to set date at midnight/noon (atStartOfDayTest) • Similar way to use instant time • Easier to format and ISO dates supported right-out-the- box
25. Java 8 • How can I find the number of years between two dates • Get next wednesday • Calculate flight time
26. Java 8 • Lambda expressions! (at last) o Anonymous functions with special properties
27. Java 8 (int x, int y) -> { return x + y; }
28. Java 8 (x, y) -> { return x + y; }
29. Java 8 (x, y) -> x + y
30. Java 8 () -> x
31. Java 8 System.out.println(message)
32. Java 8 Implements a functional interface
33. Java 8 Classic Iteration
34. Java 8 for (final String text : strings) { doSomething(text); } strings.forEach(this::doSometh ing); OLDER JAVA JAVA 8
35. Java 8 Classic Filtering (and no-reuse)
36. Java 8 List<String> longWords = new ArrayList<String>(); for (final String text : strings) { if (text.length() > 3) { longWords.add(text); } } List<String> longWords = strings.stream(). filter(e -> e.length() > 3) .collect(Collectors.<String> toList()); OLDER JAVA JAVA 8
37. Java 8 Streams!
38. Java 8 Integer maxCool = 0; User coolestUser = null; for (User user : coolUsers) { if (maxCool <= user.getCoolnessFactor()) { coolestUser = user; } } User coolestUser = coolUsers.stream(). reduce(this::coolest).get(); OLDER JAVA JAVA 8
39. Java 8 Optional
40. Java 8 Infinite Streams (Lazy)
41. Java 8 Parallelizable Operations
42. Java 8 • More expressive language • Generalization • Composability • Internal vs External iteration • Laziness & parallelism • Reusability
43. The Future? • 2014 is right around the corner… • Java 9, 2016? o Modularization (project Jigsaw) o Money and Currency API o Hope it is not this.
44. References • Examples in github • JDK 8 early access & eclipse with Java 8 support (+plugin) • Slides that inspired this talk • Quick survey of Java 7 features • Quick survey of Java 8 features • New Date and Time API • Good presentation of Java 8 • There is even a book (wait, Java 8 isn’t live yet!)
45. Evolution Of Java From Java 5 to 8