My top 10 features in Java SE 7

1. Java SE 7 {finally} 2011-08-18 Andreas Enbohm

2. 19 augusti 2011 Sida 2 Java SE 7 A evolutionaryevolement of Java 6 yearssince last update Somethingsleftout, will briefly discuss this at the end Oracle reallypushing Java forward- a lotpolitical problems with Sun made Java 7 postphonedseveraltimes Java still growing (1.42%), #1 mostusedlanguageaccording to TIOBE with 19.4% (Aug 2011) My top 10 new features (not ordered in anyway)

3. Java SE 7 – Language Changes Number 1:Try-with-resources Statement (or ARM-blocks) Before : 19 augusti 2011 Sida 3 static String readFirstLineFromFileWithFinallyBlock(String path) throwsIOException { BufferedReaderbr = new BufferedReader(new FileReader(path)); try { returnbr.readLine(); } finally { if (br != null) { try { br.close(); } catch (IOExceptionignore){ //donothing } } } }

4. Java SE 7 – Language Changes Number 1:Try-with-resources Statement (or ARM-blocks) With Java 7: 19 augusti 2011 Sida 4 static String readFirstLineFromFile(String path) throws IOException { try (BufferedReaderbr = new BufferedReader(new FileReader(path))) { return br.readLine(); } }

5. Java SE 7 – Language Changes Number 1 - NOTE: The try-with-resources statement is a try statement that declares one or more resources. A resource is as an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement. Any object that implements java.lang.AutoCloseable, which includes all objects which implement java.io.Closeable, can be used as a resource. 19 augusti 2011 Sida 5

6. Java SE 7 – Language Changes Number 2: Strings in switch Statements 19 augusti 2011 Sida 6 public String getTypeOfDayWithSwitchStatement(String dayOfWeekArg) { String typeOfDay; switch (dayOfWeekArg) { case "Monday": typeOfDay = "Start of work week"; break; case "Tuesday": case "Wednesday": case "Thursday": typeOfDay = "Midweek"; break; case "Friday": typeOfDay = "End of work week"; break; case "Saturday": case "Sunday": typeOfDay = "Weekend"; break; default: throw new IllegalArgumentException("Invalid day of the week: " + dayOfWeekArg); } return typeOfDay; }

7. Java SE 7 – Language Changes Number 2 - NOTE: The Java compiler generates generally more efficient bytecode from switch statements that use String objects than from chained if-then-else statements. 19 augusti 2011 Sida 7

8. Java SE 7 – Language Changes Number 3:Catching Multiple ExceptionTypes Before : Difficult to eliminatecodeduplicationdue to different exceptions! 19 augusti 2011 Sida 8 try { … } catch (IOException ex) { logger.log(ex); throw ex; } catch (SQLException ex) { logger.log(ex); throw ex; }

9. Java SE 7 – Language Changes Number 3:Catching Multiple ExceptionTypes With Java 7 : 19 augusti 2011 Sida 9 try { … } catch (IOException|SQLException ex) { logger.log(ex); throw ex; }

10. Java SE 7 – Language Changes Number 3 - NOTE:Catching Multiple ExceptionTypes Bytecode generated by compiling a catch block that handles multiple exception types will be smaller (and thus superior) than compiling many catch blocks that handle only one exception type each. 19 augusti 2011 Sida 10

11. Java SE 7 – Language Changes Number 4:TypeInference for GenericInstance Creation Before: Howmanytimeshave you swornabout this duplicatedcode?  19 augusti 2011 Sida 11 Map<String, List<String>> myMap = new HashMap<String, List<String>>();

12. Java SE 7 – Language Changes Number 4:TypeInference for GenericInstance Creation With Java 7: 19 augusti 2011 Sida 12 Map<String, List<String>> myMap = new HashMap<>();

13. Java SE 7 – Language Changes Number 4 - NOTE:TypeInference for GenericInstance Creation Writing new HashMap() (withoutdiamond operator) will still use the rawtype of HashMap (compilerwarning) 19 augusti 2011 Sida 13

14. Java SE 7 – Language Changes Number 5:Underscores in NumericLiterals 19 augusti 2011 Sida 14 longcreditCardNumber = 1234_5678_9012_3456L; longsocialSecurityNumber = 1977_05_18_3312L; float pi = 3.14_15F; longhexBytes = 0xFF_EC_DE_5E; longhexWords = 0xCAFE_BABE; longmaxLong = 0x7fff_ffff_ffff_ffffL; long bytes = 0b11010010_01101001_10010100_10010010;

15. Java SE 7 – Language Changes Number 5 - NOTE:Underscores in NumericLiterals You can place underscores only between digits; you cannot place underscores in the following places: At the beginning or end of a number Adjacent to a decimal point in a floating point literal Prior to an F or L suffix In positions where a string of digits is expected 19 augusti 2011 Sida 15

16. Java SE 7 – ConcurrentUtilities Number 6:Fork/JoinFramework (JSR 166) ” a lightweightfork/joinframework with flexible and reusablesynchronizationbarriers, transfer queues, concurrent linked double-endedqueues, and thread-localpseudo-random-number generators.” 19 augusti 2011 Sida 16

17. Java SE 7 – ConcurrentUtilities Number 6:Fork/JoinFramework (JSR 166) 19 augusti 2011 Sida 17 if (my portion of the work is small enough) do the work directly else split my work into two pieces invoke the two pieces and wait for the results

18. Java SE 7 – ConcurrentUtilities Number 6:Fork/JoinFramework (JSR 166) 19 augusti 2011 Sida 18

20. RecursiveTask

21. RecursiveAction

22. ThreadLocalRandom

23. ForkJoinPool19 augusti 2011 Sida 19

24. Java SE 7 – Filesystem API Number 7: NIO 2 Filesystem API (Non-Blocking I/O) Bettersupports for accessingfile systems such and support for customfile systems (e.g. cloudfile systems) Access to metadata such as file permissions Moreeffecient support whencopy/movingfiles EnchancedExceptionswhenworking on files, i.e. file.delete() nowthrowsIOException (not just Exception) 19 augusti 2011 Sida 20

25. Java SE 7 – JVM Enhancement Number 8:InvokeDynamic (JSR292) Support for dynamiclanguages so theirperformance levels is near to that of the Java language itself At byte code level this means a new operand (instruction) called invokedynamic Make is possible to do efficient method invocation for dynamic languages (such as JRuby) instead of statically (like Java) . Huge performance gain 19 augusti 2011 Sida 21

26. Java SE 7 – JVM Enhancement Number 9: G1 and JVM optimization G1 morepredictable and uses multiple coresbetterthan CMS Tiered Compilation –Bothclient and server JIT compilers are usedduringstarup NUMA optimization - Parallel Scavenger garbage collector has been extended to take advantage of machines with NUMA (~35% performance gain) EscapeAnalysis - analyze the scope of a new object's and decide whether to allocate it on the Java heap 19 augusti 2011 Sida 22

27. Java SE 7 – JVM Enhancement Number 9:EscapeAnalysis 19 augusti 2011 Sida 23 public class Person { private String name; private int age; public Person(String personName, intpersonAge) { name = personName; age = personAge; } public Person(Person p) { this(p.getName(), p.getAge()); } } public classEmployee { private Person person; // makes a defensive copy to protectagainstmodifications by caller public Person getPerson() { return new Person(person) }; public voidprintEmployeeDetail(Employeeemp) { Person person = emp.getPerson(); // this callerdoes not modify the object, so defensive copywasunnecessary System.out.println ("Employee'sname: " + person.getName() + "; age: " + person.getAge()); } }

28. Java SE 7 - Networking Number 10: Support for SDP  SocketDirectProtocol (SDP) enablesJVMs to use Remote Direct Memory Access (RDMA). RDMA enables moving data directly from the memory of one computer to another computer, bypassing the operating system of both computers and resulting in significant performance gains. The result is High throughput and Low latency (minimal delay between processing input and providing output) such as you would expect in a real-time application. 19 augusti 2011 Sida 24

29. Java SE 7 - Networking Number 10 - NOTE: Support for SDP The Sockets Direct Protocol (SDP) is a networking protocol developed to support stream connections over InfiniBand fabric. Solaris 10 5/08 has support for InfiniBand fabric (which enables RDMA). On Linux, the InfiniBand package is called OFED (OpenFabrics Enterprise Distribution). 19 augusti 2011 Sida 25

30. Java SE 7 A complete list of all new features can be seen on http://www.oracle.com/technetwork/java/javase/jdk7-relnotes-418459.html 19 augusti 2011 Sida 26

31. Java SE 8 Some features whereleftout in Java 7; mostimportant are Project Lambda (closures) and Project Jigsaw (modules) targeted for Java 8 (late 2012) Lambdas (and extension methods) willprobably be the biggestsinglechangeevermade on the JVM. Will introduce a powerfulprogrammingmodel, however it comes with a great deal of complexity as well. Moduleswillmade it easier to version modules (no moreJAR-hell) and introducea new way of definingclasspaths 19 augusti 2011 Sida 27

32. Java SE 7 & 8 Questions? 19 augusti 2011 Sida 28