What`s New in Java 8
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This document provides an overview and summary of new features in Java 8. It begins with the schedule and release dates for Java 8 from 2012 to 2014. The major changes covered include lambda expressions, which allow passing code as data and are enabled by default functional interfaces. The new date/time API provides a modern replacement for the legacy Date/Calendar APIs. Type annotations allow adding metadata to types. Compact profiles define modular class libraries. Overall, Java 8 aims to better support parallel programming through new language features and library APIs.
![Why Can`t We Forget About Parallelism?
Most of parallelism problems are doing bulk operations on
collection
and we keep writing code like this:
int sum = 0;
for (int i = 0; i < a.length; i++) {
sum += a[i];
}
It is inherently serial](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-19-320.jpg)
![Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
We`re going to write this:
int sum = 0;
int [] sum = new int[1];
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
myList.forEach(
…
);](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-28-320.jpg)
![Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
We`re going to write this:
int sum = 0;
int [] sum = new int[1];
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
myList.forEach(
…
);
• Let the collection choose its iteration strategy
- Parallel, serial, out-of-order, lazy, …](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-29-320.jpg)
![Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
We`re going to write this:
int sum = 0;
int [] sum = new int[1];
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
myList.forEach(
a -> sum[0]+=a
);
• Let the collection choose its iteration strategy
- Parallel, serial, out-of-order, lazy, …](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-30-320.jpg)
![Why Can`t We Forget About Parallelism?
a ->
sum[0]+=a](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-31-320.jpg)
![What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
a return
type
a ->
having an
argument
list
and a body
sum[0]+=a](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-37-320.jpg)
![What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
having an
argument
list
a return
type
and a body
and able to refer to values from the enclosing scope (closure)
a ->
sum[0]+=a](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-38-320.jpg)
![What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
having an
argument
list
To pass behavior to the API as data
a return
type
and a body
and able to refer to values from the enclosing scope (closure)
a ->
sum[0]+=a](https://image.slidesharecdn.com/jdk8-zainalpour-140111111338-phpapp02/85/What-s-New-in-Java-8-39-320.jpg)
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What`s New in Java 8
- 1. What`s New in Java 8 Mohsen Zainalpour [email protected] JUG
- 2. JDK 8 Schedule and status • • • • • • • • • • 2012/04/26 2012/06/14 2012/08/02 2012/09/13 2012/11/29 2013/01/31 2013/06/13 2013/09/05 2014/01/23 2014/03/18 M1 M2 M3 M4 M5 M6 M7 Feature Complete M8 Developer Preview M9 Final Release Candidate GA General Availability
- 3. Agenda Major changes 1 Why is Java still changing? 2 Lambda Project 3 Date and Time API 4 Type Annotations 5 Compact Profiles JUG
- 4. Java 8 Is Revolutionary, Java Is Back “Lambda is the single largest upgrade to the programming model. Ever. It's larger even than Generics. It's the first time since the beginning of Java that we've done a carefully coordinated co-evolution of the virtual machine, the language and the libraries, all together. Yet the result still feels like Java. Mark Reinhold (Chief Architect of the Java Platform Group at Oracle)
- 5. Java 8 Is Revolutionary, Java Is Back “Lambda is the single largest upgrade to the programming model. Ever. It's larger even than Generics. It's the first time since the beginning of Java that we've done a carefully coordinated co-evolution of the virtual machine, the language and the libraries, all together. Yet the result still feels like Java. Mark Reinhold (Chief Architect of the Java Platform Group at Oracle)
- 7. Why is Java still changing?
- 8. Why is Java still changing?
- 9. Why is Java still changing?
- 10. Why is Java still changing?
- 11. Why is Java still changing?
- 12. Why is Java still changing?
- 13. Why is Java still changing?
- 14. Why is Java still changing? The changing computing background big data multicore cloud computing Increasingly dealing with big data (terabytes and up) and wishing to exploit multicore computers or computing clusters effectively to process this. And this means using: parallel processing
- 15. The Progress of Programming There`s been a lot of progress & Progress is being allowed to forget things!
- 16. The Progress of Programming There`s been a lot of progress: - Assemblers let us forget opcodes
- 17. The Progress of Programming There`s been a lot of progress: - Assemblers let us forget opcodes - Garbage collections let us forget memory management #include <stdio.h> #include <stdlib.h> int main () { … buffer = (char*) malloc (i+1); … free (buffer); … }
- 18. The Progress of Programming So what about parallelism?
- 19. Why Can`t We Forget About Parallelism? Most of parallelism problems are doing bulk operations on collection and we keep writing code like this: int sum = 0; for (int i = 0; i < a.length; i++) { sum += a[i]; } It is inherently serial
- 20. Why Can`t We Forget About Parallelism? If the processing of different elements is to proceed in parallel, it is the responsibility of the client code
- 21. Why Can`t We Forget About Parallelism? If the processing of different elements is to proceed in parallel, it is the responsibility of the client code n1 n2 n3 sum1 n4 n5 n6 n7 sum2 n8 n9 … … sum3 … … sum4
- 22. Why Can`t We Forget About Parallelism? If the processing of different elements is to proceed in parallel, it is the responsibility of the client code n1 n2 n3 sum1 n4 n5 n6 n7 sum2 n8 n9 … … … … sum3 class Sum implements Callable<Long> { private final long from; private final long to; Sum(long from, long to) { this.from = from; this.to = to; } public Long call() { long acc = 0; for (long i = from; i <= to; i++) { acc = acc + i; } return acc; } } sum4
- 23. Why Can`t We Forget About Parallelism? If the processing of different elements is to proceed in parallel, it is the responsibility of the client code n1 n2 n3 sum1 n4 n5 n6 n7 sum2 n8 n9 … … sum3 … … sum4 ExecutorService executor = Executors.newFixedThreadPool(2); List<Future<Long>> results = executor.invokeAll(asList( new Sum(1, 250), new Sum(251, 500), new Sum(551, 750), new Sum(751, 1000) )); for (Future<Long> result : results) { System.out.println(result.get()); }
- 24. Why Can`t We Forget About Parallelism? Sequential Thread 1 Parallel (assuming a quad core machine) Thread 1 Thread 2 Thread 3 Thread 4 Time t Done parallel Done sequential
- 25. Why Can`t We Forget About Parallelism? Let the Library Writers do it! Collection developers know the recursive structure of their data But right now they can`t use that knowledge
- 26. Why Can`t We Forget About Parallelism? Let the Library Writers do it! Collection developers know the recursive structure of their data But right now they can`t use that knowledge int sum = 0; for (Iterator<Integer> itr = myList.iterator();itr.hasNext(); ) { sum += itr.next(); } The problem is external iteration
- 27. Why Can`t We Forget About Parallelism? Internal Iteration Instead of this: int sum = 0; for (int i=0;i<myList.size();i++){ int a=myList.get(i); sum+=a; }
- 28. Why Can`t We Forget About Parallelism? Internal Iteration Instead of this: We`re going to write this: int sum = 0; int [] sum = new int[1]; for (int i=0;i<myList.size();i++){ int a=myList.get(i); sum+=a; } myList.forEach( … );
- 29. Why Can`t We Forget About Parallelism? Internal Iteration Instead of this: We`re going to write this: int sum = 0; int [] sum = new int[1]; for (int i=0;i<myList.size();i++){ int a=myList.get(i); sum+=a; } myList.forEach( … ); • Let the collection choose its iteration strategy - Parallel, serial, out-of-order, lazy, …
- 30. Why Can`t We Forget About Parallelism? Internal Iteration Instead of this: We`re going to write this: int sum = 0; int [] sum = new int[1]; for (int i=0;i<myList.size();i++){ int a=myList.get(i); sum+=a; } myList.forEach( a -> sum[0]+=a ); • Let the collection choose its iteration strategy - Parallel, serial, out-of-order, lazy, …
- 31. Why Can`t We Forget About Parallelism? a -> sum[0]+=a
- 32. Lambda Project – JSR 335 JSR 335 (Lambda Project) aims to support programming in a multicore environment by adding closures and related features to the Java language.
- 33. What are Lambda Expressions (closures)? A lambda expression :
- 34. What are Lambda Expressions (closures)? A lambda expression : is an anonymous method
- 35. What are Lambda Expressions (closures)? A lambda expression : is an anonymous method a -> having an argument list
- 36. What are Lambda Expressions (closures)? A lambda expression : is an anonymous method a return type a -> having an argument list
- 37. What are Lambda Expressions (closures)? A lambda expression : is an anonymous method a return type a -> having an argument list and a body sum[0]+=a
- 38. What are Lambda Expressions (closures)? A lambda expression : is an anonymous method having an argument list a return type and a body and able to refer to values from the enclosing scope (closure) a -> sum[0]+=a
- 39. What are Lambda Expressions (closures)? A lambda expression : is an anonymous method having an argument list To pass behavior to the API as data a return type and a body and able to refer to values from the enclosing scope (closure) a -> sum[0]+=a
- 40. From Single Method Interface …. public interface Comparator<T> { }
- 41. From Single Method Interface …. public interface Comparator<T> { int compare(T o1, T o2); }
- 42. From Single Method Interface …. public interface Comparator<T> { int compare(T o1, T o2); Single Abstract Method (SAM) }
- 43. From Single Method Interface …. public interface Comparator<T> { int compare(T o1, T o2); Single Abstract Method (SAM) } Functional Interface
- 44. From Single Method Interface …. public interface Comparator<T> { int compare(T o1, T o2); } Collections.sort(strings, new Comparator<String>() { public int compare(String s1, String s2) { return s1.compareToIgnoreCase(s2); } });
- 45. From Single Method Interface …. public interface Comparator<T> { int compare(T o1, T o2); } Collections.sort(strings, new Comparator<String>() { public int compare(String s1, String s2) { return s1.compareToIgnoreCase(s2); } });
- 46. From Single Method Interface …. public interface Comparator<T> { int compare(T o1, T o2); } Collections.sort(strings, new Comparator<String>() { public int compare(String s1, String s2) { return s1.compareToIgnoreCase(s2); } }); Bulky syntax Confusion surrounding the meaning of names and this
- 47. … To Lambda Expressions Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2));
- 48. … To Lambda Expressions Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2));
- 49. … To Lambda Expressions Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2)); Lambda expression are always converted to instance of a functional interface Comparator<String> c = (s1, s2) -> s1.compareToIgnoreCase(s2)); No need of changing the JVM to create a new type for lambda expressions
- 50. … To Lambda Expressions Collections.sort(strings, new Comparator<String>() { public int compare(String s1, String s2) { return s1.compareToIgnoreCase(s2); } }); Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2) );
- 51. … To Lambda Expressions Collections.sort(strings, new Comparator<String>() { public int compare(String s1, String s2) { return s1.compareToIgnoreCase(s2); } }); Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2) );
- 52. Without more language support for parallel idioms, people will instinctively reach for serial idioms
- 53. External Iteration Sum of squares long sum = 0L; for (long i = 0; i < N; i++) { sum += i * i; }
- 54. Internal Iteration Sum of squares long sum = LongStream.range(0, N) .map(i -> i * i) .sum();
- 55. Internal Iteration Going parallel long sum = LongStream.range(0, N) .parallel() .map(i -> i * i) .sum();
- 56. Parallel Streams A behavioral parameter (lambda) may be invoked concurrently – This constraint gives us “wiggle room” to optimize
- 57. Up the level of abstraction External iteration conflates what with how Internal iteration: more what; less how Client passes behavior to the API as data Library is free to use Multiple threads Out-oforder execution Laziness
- 58. Lambdas in Java 8 Code as data (Simplicity) Bulk data operations Lambda Interface evolution Multi-core processing / parallel processing
- 59. Lambdas in Java 8
- 60. Date and Time API JSR 310
- 61. New Date and Time API History of Java Date/Time APIs Java.util.Date, java.util.Calendar - Strong candidates for the all-time worst Java platform library design Joda Time - Quality date and time library JSR-310 - Builds on experience of Joda Time
- 62. New Date and Time API Design Principles Immutable - Thread-safe, allows caching Fluent - easy to read, like a DSL LocalDate.of(2013,Month.JANUARY,09).withYear(2014);
- 63. New Date and Time API Time for Humans Field-base, designed for humans - Year,month,day,hour,minute,second - LocalDate,LocalDateTime,ZonedDateTime,Period …
- 64. New Date and Time API Los Angeles 16:20 London 12:50
- 65. New Date and Time API void flightTime() { LocalDate date = LocalDate.of(2013, Month.SEPTEMBER, 14); LocalTime takeoff = LocalTime.of(12, 50); LocalTime landing = LocalTime.of(16, 20); ZoneId LHR = ZoneId.of("Europe/London"); ZoneId SFO = ZoneId.of("America/Los_Angeles"); Duration flightTime = Duration.between( ZonedDateTime.of(date, takeoff, LHR), ZonedDateTime.of(date, landing, SFO)); System.out.println("Flight time: " + flightTime); }
- 67. 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 { ... }
- 68. Repeating Annotations Before @Schedules ({ @Schedule(dayOfMonth="Last"), @Schedule(dayOfWeek="Fri", hour="23") )} public void doPeriodicCleanup() { ... }
- 69. 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() { ... }
- 70. Java SE 8 Compact Profiles
- 71. Java SE 8 Compact Profiles SE 8 Compact Profiles 3 SE Full JRE Optional Components UI & Toolkits 2 Compact3 Class libraries Integration Libraries Compact2 Class libraries Other Base Libraries Base Compact1 Classes Lang & Util Base Libraries Hotspot VM Hotspot VM 1
- 72. Q&A
- 73. 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-modernmainstream-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
- 74. 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