![Problem
String[] names = {"Alice", "Bob", "Charlie", Dave"};
Arrays.sort(names, new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
return o1.compareToIgnoreCase(o2);
}
});](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-6-320.jpg)
!["tiny" anonymous inner
class
String[] names = {"Alice", "Bob", "Charlie", Dave"};
Arrays.sort(names, new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
return o1.compareToIgnoreCase(o2);
}
});](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-7-320.jpg)
![All we need!
String[] names = {"Alice", "Bob", "Charlie", Dave"};
Arrays.sort(names, new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
return o1.compareToIgnoreCase(o2);
}
});](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-9-320.jpg)
![Solution - closure
String[] names = {"Alice", "Bob", "Charlie", Dave"};
Arrays.sort(names, (o1, o2) -> o1.compareToIgnoreCase(o2));](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-10-320.jpg)
![Method References
String[] names = {"Alice", "Bob", "Charlie", Dave"};
Arrays.sort(names,
(o1, o2) -> o1.compareToIgnoreCase(o2));
//translates to
String[] names = {"Alice", "Bob", "Charlie", Dave"};
Arrays.sort(names, String::compareToIgnoreCase);](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-25-320.jpg)
![Example
String[] names = {"Alice", "Bob", "Charlie", "Dave"};
List<String> filteredNames = Streams.stream(names)
.filter(e -> e.length() >= 4)
.into(new ArrayList<>());
filteredNames.stream().forEach(System.out::println);](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-32-320.jpg)
![Example: JSR 310
Clock clock = Clock.systemUTC();
LocalDate localDate = LocalDate.now(clock);
//2012-11-13
MonthDay brasilBday = MonthDay.of(JUNE, 21);
ZoneId zoneId = ZoneId.of("America/New_York");
Clock clock = Clock.system(zoneId);
ZonedDateTime zonedDateTimeUS = ZonedDateTime.now(clock);
//2012-11-11T04:17:58.693-05:00[America/New_York]](https://image.slidesharecdn.com/java8vilniusjug-121119043901-phpapp02/85/Java-8-62-320.jpg)
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Java 8
- 1. Java 8 Interesting parts Vaidas Pilkauskas, Kasparas Rudokas Vilnius JUG
- 2. Agenda ● Lambda ● Date & Time ● PermGen ● Annotations
- 4. lambda vs. closure A lambda is just an anonymous function. myCollection.filter(e ‑> e.length() >= 5) A closure is any function which closes over the environment in which it was defined. This means that it can access variables not in its parameter list. int minLength = 5; myCollection.filter(new Predicate(){ boolean apply(MyElement e) { return e != null ? e.length >= minLength : false; } })
- 5. Project Lambda (JSR 335) ● Language changes ○ Lambda Expression ○ Virtual Extension Method ● Library changes ○ Functional API ○ Parallel collections ○ Bulk Operations
- 6. Problem String[] names = {"Alice", "Bob", "Charlie", Dave"}; Arrays.sort(names, new Comparator<String>() { @Override public int compare(String o1, String o2) { return o1.compareToIgnoreCase(o2); } });
- 7. "tiny" anonymous inner class String[] names = {"Alice", "Bob", "Charlie", Dave"}; Arrays.sort(names, new Comparator<String>() { @Override public int compare(String o1, String o2) { return o1.compareToIgnoreCase(o2); } });
- 8. "tiny" and useful ● callbacks ● runnables ● event handlers ● comparators ● ...and many other cases
- 9. All we need! String[] names = {"Alice", "Bob", "Charlie", Dave"}; Arrays.sort(names, new Comparator<String>() { @Override public int compare(String o1, String o2) { return o1.compareToIgnoreCase(o2); } });
- 10. Solution - closure String[] names = {"Alice", "Bob", "Charlie", Dave"}; Arrays.sort(names, (o1, o2) -> o1.compareToIgnoreCase(o2));
- 11. What do we mean by closures? ● a unit of deferred execution ● code that can be passed as a value ● can be used in an assignment statement ● capture of a surrounding environment
- 12. Lambda Expressions s -> s.length() (int x, int y) -> x+y () -> 42 (x, y, z) -> { if (x == y) return x; else { int result = y; for (int i = 1; i < z; i++) result *= i; return result; } }
- 13. Lambda Syntax principally because something similar has been generally well-received in other Java-like languages (C# and Scala), and a clearly "better" alternative did not present itself
- 14. Lambda ● Effectively final variables
- 15. Lambda ● Effectively final variables ● Shadowing
- 16. Lambda ● Effectively final variables ● Shadowing ● break, continue must be local
- 17. Lambda ● Effectively final variables ● Shadowing ● break, continue must be local ● this - lambda is not an instance method. (this == surrounding context object)
- 18. Lambda ● Effectively final variables ● Shadowing ● break, continue must be local ● this - lambda is not an instance method. (this == surrounding context object) ● throw completes method abruptly
- 19. Functional Interfaces A functional interface is an interface that has just one abstract method, and thus represents a single function contract.
- 20. Functional Interfaces SAM - Single Abstract Method interfaces one method excluding Object methods interface Runnable { void run(); } // Functional interface Foo { boolean equals(Object obj); } // Not functional; equals is already an implicit member interface Comparator<T> { boolean equals(Object obj); int compare(T o1, T o2); } // Functional; Comparator has one abstract non-Object method
- 21. Method References Method reference is a shorthand for a lambda invoking just that method System::getProperty "abc"::length String::length super::toString ArrayList::new Arrays.sort(ints, Integer::compareTo);
- 22. Method References Static methods simply translate like lambda with same arguments and return type class Math { public static int max(int a, int b) {...} } interface Operator<T> { T eval(T left, T right); } Operator<Integer> lambda = (a, b) -> Math.max(a, b); Operator<Integer> methodRef = Math::max;
- 23. Method References Non static method reference of type T translates like lambda with an additional argument of type T Comparator<String> c = (s1, s2) -> s1.compareToIgnoreCase (s2); //translates to: Comparator<String> c = String::compareToIgnoreCase;
- 24. Method References Instance method reference translates like lambda with same arguments and return type (and implicit receiver) Callable<Integer> l = () -> "boo".length(); //translates to: Callable<Integer> c = "boo"::length;
- 25. Method References String[] names = {"Alice", "Bob", "Charlie", Dave"}; Arrays.sort(names, (o1, o2) -> o1.compareToIgnoreCase(o2)); //translates to String[] names = {"Alice", "Bob", "Charlie", Dave"}; Arrays.sort(names, String::compareToIgnoreCase);
- 26. Compatibility Cannot add new interface methods (without forcing current interface users to implement them) But we need new lambda enabled methods (on Java core libraries!)
- 27. Default methods (also known as) ● virtual extension methods ● defender methods
- 28. Default methods interface NormalInterface { void myNormalMethod(); void myDefaultMethod () default { System.out.println("-> myDefaultMethod"); } } class NormalInterfaceImpl implements NormalInterface { @Override public void myNormalMethod() { System.out.println("-> myNormalMethod"); } }
- 29. Functional Collections Major changes in collection API: ● Internal iteration support with Iterable/Stream interfaces (forEach, filter, map, etc)
- 30. Functional Collections Major changes in collection API: ● Internal iteration support with Iterable/Stream interfaces (forEach, filter, map, etc) ● Explicit parallel APIs for greater parallelism support. These can be combined with Fork/Join to divide the tasks
- 31. Functional Collections Major changes in collection API: ● Internal iteration support with Iterable/Stream interfaces (forEach, filter, map, etc) ● Explicit parallel APIs for greater parallelism support. These can be combined with Fork/Join to divide the tasks ● Greater stress on immutability and avoiding in-place mutation which was done in the conventional for-each loops
- 32. Example String[] names = {"Alice", "Bob", "Charlie", "Dave"}; List<String> filteredNames = Streams.stream(names) .filter(e -> e.length() >= 4) .into(new ArrayList<>()); filteredNames.stream().forEach(System.out::println);
- 33. Streams ● No storage - nothing is stored in stream
- 34. Streams ● No storage - nothing is stored in stream ● Functional in nature - new values are produced
- 35. Streams ● No storage - nothing is stored in stream ● Functional in nature - new values are produced ● Laziness-seeking. Many operations can be implemented lazily
- 36. Streams ● No storage - nothing is stored in stream ● Functional in nature - new values are produced ● Laziness-seeking. Many operations can be implemented lazily ● Bounds optional. Think of infinite stream
- 37. Functional interfaces java.util.functions ● Predicate - a property of the object passed as argument ● Block - an action to be performed with the object passed as argument ● Mapper - transform a T to a U ● ...
- 38. Parallelism //sequential int sum = myCollection.stream() .filter(b -> b.getColor() == BLUE) .map(b -> b.getWeight()) .sum(); //parallel int sum = myCollection.parallel() .filter(b -> b.getColor() == BLUE) .map(b -> b.getWeight()) .sum();
- 39. Advantages ● Elements may be computed lazily. If we apply a Mapper to a collection of a thousand elements but only iterate over the first three, the remaining elements will never be mapped.
- 40. Advantages ● Elements may be computed lazily. If we apply a Mapper to a collection of a thousand elements but only iterate over the first three, the remaining elements will never be mapped. ● Method chaining is encouraged. Hence there's no need to store intermediate results in their own collections.
- 41. Advantages ● Elements may be computed lazily. If we apply a Mapper to a collection of a thousand elements but only iterate over the first three, the remaining elements will never be mapped. ● Method chaining is encouraged. Hence there's no need to store intermediate results in their own collections. ● Internal iteration hides implementation decisions. For example, we could parallelize a map() operation just by writing myCollection.parallel().map(e ‑> e.length()).
- 42. Try it out today! The prototype compiler is being implemented in OpenJDK. ● Source code is available at http://hg.openjdk.java. net/lambda/lambda ● Binary snapshots of the lambda-enabled JDK prototype are available athttp://jdk8.java.net/lambda IDE support: ● Netbeans 8 Nightly Builds with experimental Lambda support ● IDEA 12 EAP with experimental Lambda support
- 43. Date & Time API JSR 310
- 45. Oldies: Date ● Mutable ● Years being indexed from 1900
- 46. Oldies: Date ● Mutable ● Years being indexed from 1900 ● Months being indexed from 0
- 47. Oldies: Date ● Mutable ● Years being indexed from 1900 ● Months being indexed from 0 Ex.: Date d = new Date(1L); System.out.println(d.toString());
- 48. Oldies: Date ● Mutable ● Years being indexed from 1900 ● Months being indexed from 0 Ex.: Date d = new Date(1L); System.out.println(d.toString()); //Thu Jan 01 02:00:00 EET 1970
- 50. Oldies: Calendar ● Mutable ● Not very convenient (lack of simple field methods)
- 51. Oldies: Calendar ● Mutable ● Not very convenient (lack of simple field methods) ● Very difficult to extend (add new calendars)
- 52. Oldies: Calendar ● Mutable ● Not very convenient (lack of simple field methods) ● Very difficult to extend (add new calendars) Ex.: Calendar c = Calendar.getInstance(); int weekday = c.get(DAY_OF_WEEK);
- 53. Oldies: Calendar ● Mutable ● Not very convenient (lack of simple field methods) ● Very difficult to extend (add new calendars) Ex.: Calendar c = Calendar.getInstance(); int weekday = c.get(DAY_OF_WEEK); Date d = c.getTime();
- 56. JSR 310 ● Immutable ● Defines consistent language for domain ○ Offset from UTC vs TimeZone ○ Machine vs Human ○ ISO 8601
- 57. JSR 310 ● Immutable ● Defines consistent language for domain ○ Offset from UTC vs TimeZone ○ Machine vs Human ○ ISO 8601 ● No old Date/Calendar usage (clean)
- 58. JSR 310 ● Immutable ● Defines consistent language for domain ○ Offset from UTC vs TimeZone ○ Machine vs Human ○ ISO 8601 ● No old Date/Calendar usage (clean) ● Extensible
- 59. JSR 310 ● Immutable ● Defines consistent language for domain ○ Offset from UTC vs TimeZone ○ Machine vs Human ○ ISO 8601 ● No old Date/Calendar usage (clean) ● Extensible ● Led by JodaTime creator (S. Colebourne)
- 60. Example: JSR 310 Clock clock = Clock.systemUTC(); LocalDate localDate = LocalDate.now(clock); //2012-11-13
- 61. Example: JSR 310 Clock clock = Clock.systemUTC(); LocalDate localDate = LocalDate.now(clock); //2012-11-13 MonthDay brasilBday = MonthDay.of(JUNE, 21);
- 62. Example: JSR 310 Clock clock = Clock.systemUTC(); LocalDate localDate = LocalDate.now(clock); //2012-11-13 MonthDay brasilBday = MonthDay.of(JUNE, 21); ZoneId zoneId = ZoneId.of("America/New_York"); Clock clock = Clock.system(zoneId); ZonedDateTime zonedDateTimeUS = ZonedDateTime.now(clock); //2012-11-11T04:17:58.693-05:00[America/New_York]
- 63. Example: JSR 310 import static javax.time.calendrical.LocalPeriodUnit. HOURS; Period p = Period.of(5, HOURS); LocalTime time = LocalTime.now(); LocalTime newTime; newTime = time.plus(5, HOURS); // or newTime = time.plusHours(5); // or newTime = time.plus(p);
- 64. Why not Joda Time? ● Machine timelines ● Pluggable chronology ● Nulls ● Internal implementation
- 65. VM/GC JEP 122 & JEP 156
- 66. PermGen removal ● Java Heap vs PermGen
- 67. PermGen removal ● Java Heap vs PermGen
- 68. PermGen removal ● Java Heap vs PermGen ● Why it was required anyway?
- 69. PermGen removal ● Java Heap vs PermGen ● Why it was required anyway? ● So what?
- 70. Annotations JSR 308 & JEP 120
- 71. Type Annotations ● In Java 7 we have annotations on declarations Ex.: class SomeClass { … } class ListElement<E> { … } public void v() (int I) { long l; {
- 72. Type Annotations ● JSR-308 brings annotations on Type use ● Are an enabler for the checkers framework Ex.: new @Interned MyObject(); myString = (@NonNull String) myObject; void monitorTemperature() throws @Critical TemperatureException { ... }
- 73. Repeating Annotations ● Before @Schedules ({ @Schedule(dayOfMonth="Last"), @Schedule(dayOfWeek="Fri", hour="23") ({ public void doPeriodicCleanup() { ... }
- 74. Repeating Annotations ● Before @Schedules ({ @Schedule(dayOfMonth="Last"), @Schedule(dayOfWeek="Fri", hour="23") ({ public void doPeriodicCleanup() { ... } ● After @Schedule(dayOfMonth="Last”) @Schedule(dayOfWeek="Fri", hour="23") public void doPeriodicCleanup() { ... }
- 75. Q&A
- 76. References * Lambda http://stackoverflow.com/questions/220658/what-is-the-difference-between-a-closure-and-a-lambda http://openjdk.java.net/projects/lambda/ http://jcp.org/aboutJava/communityprocess/edr/jsr335/index2.html http://vimeo.com/48577033 (slides: http://www.slideshare.net/tkowalcz/java-gets-a-closure) http://datumedge.blogspot.co.uk/2012/06/java-8-lambdas.html http://www.theserverside.com/news/thread.tss?thread_id=68718 http://medianetwork.oracle.com/video/player/1785479333001 https://oracleus.activeevents.com/connect/sessionDetail.ww?SESSION_ID=6080 https://oracleus.activeevents.com/connect/sessionDetail.ww?SESSION_ID=5089 http://www.lektorium.tv/lecture/?id=14048 http://www.lektorium.tv/lecture/?id=14049 http://blog.xebia.com/2012/11/05/report-will-java-8s-lambda-change-the-face-of-the-world/ http://www.slideshare.net/fsarradin/java-8-lambda http://programmers.stackexchange.com/questions/173441/what-triggered-the-popularity-of-lambda-functions-in-modern-mainstream-programmi?newsletter=1&nlcode=29983% 7c903a http://www.slideshare.net/bje/java-closures * Collections http://www.javabeat.net/2012/05/enhanced-collections-api-in-java-8-supports-lambda-expressions/ http://cr.openjdk.java.net/~briangoetz/lambda/collections-overview.html http://architects.dzone.com/articles/java-collections-api
- 77. References * Remove the Permanent Generation http://www.cubrid.org/blog/dev-platform/understanding-jvm-internals/ http://javaeesupportpatterns.blogspot.com/2011/10/java-7-features-permgen-removal.html http://java.dzone.com/articles/busting-permgen-myths https://oracleus.activeevents.com/connect/sessionDetail.ww?SESSION_ID=5135 * JSR 310: Date and Time API http://java.dzone.com/articles/introducing-new-date-and-time http://sourceforge.net/apps/mediawiki/threeten/index.php?title=ThreeTen http://www.infoq.com/news/2010/03/jsr-310 https://docs.google.com/document/pub?id=1rd8yplQZIRz3LxMzpVLuskr1b0HwBmK9PXpdgBYojSw http://sourceforge.net/apps/mediawiki/threeten/index.php?title=User_Guide https://oracleus.activeevents.com/connect/sessionDetail.ww?SESSION_ID=4350 * General Java8 http://openjdk.java.net/projects/jdk8/features http://www.pcadvisor.co.uk/news/software/3401314/oracle-java-upgrades-still-worthwhile-despite-postponed-features/ http://dhruba.name/2011/07/06/oracle-discusses-java-7-8-new-features-on-video/ http://channel9.msdn.com/Events/Lang-NEXT/Lang-NEXT-2012/Java-8 http://www.parleys.com/#st=5&id=2850&sl=1 http://www.parleys.com/#st=5&id=2847 https://oracleus.activeevents.com/connect/sessionDetail.ww?SESSION_ID=2872 https://oracleus.activeevents.com/connect/sessionDetail.ww?SESSION_ID=10458