Devoxx11: Java 7 toolbox

Project coin brought some minor improvements to the Java language. Most notably:

• easier generics:
  • diamond operator <>: less copy/paste thanks to smarter compiler
  • less warnings on vararg's
• easier error-handling:
  • multicatch: less copy/paste
  • 'try-with-resource' contstruct: automatic & correct closing and error handling
• consistency / clarity
  • Strings in Switch
  • numbers improvements:
    • direct binary format: 0b0101001
    • logical grouping of large number in sub-chunks: 123_435_576L --> java ignores the underscores.

IDE support

• Netbeans & Intellij have excellent support for Java 7
  • inline hints and refactorings are offered
  • batch refactorings throughout the 'inspect and transform' dialog
• Eclipse is somewhat lagging behind.

Devoxx 2009: Project Coin

18/11/2009, Joe D. Darcy, Sun

slides: http://blogs.sun.com/darcy/entry/project_coin_devoxx_2009

Project Coin

• small language changes in JDK7
• keep broad consideration of java landscape → remain consistent with the Java Language
• bigger language changes, not in scope of Project Coin
  • JSR308: annotations to improve static checkers (e.g. @NotNull)
  • JSR294: modularity

principles of Project Coin:

• reading more important than writing
  • 'beautiful' code
  • don't hide what's happening
• simplicity matters
• no slash-and-burn: remember broad user-base
• balance stability versus progress
• prefer library / IDE changes over language changes (String.join)
• no new keywords
• no type system changes
• small in specification, implementation and testing

methodology:

• open: blog entries / white board on Devoxx2008
• call for proposals
• prototypes recommended
  • lot of work
  • very beneficial → learn / find issues
• existing requests for enhancement: 120 changes → too much

final list of Project Coin enhancements

• numbers:
  • binary notation: 0b00100100001
  • group numbers with '_': long big = 1_123_456_789;
• switch on a String – really cool!
  • specification: only one word added
  • proposal contains a suggested implementation:
    • uses String.hashCode() for an initial switch
  • big patch in javac
  • lots of tests to validate change
    • reject pre -source 7 classes
    • null behavior
    • hash collisions
    • fall-throughs
    • → comparable to enum switch control flow
• diamond <> operator : type interference → e.g. Map <String,String> map = new HashMap<>();
  • a lot of prototyping work
  • quantitative analysis
  • some concerns on language evolution were considered
• JSR292: invokedynamic for dynamic languages
• auto-close of Closable types within a special try block (ARM)
  • try(File f = new File) {} → f is automatically closed when leaving the block
• simplified varargs method invocation, working along with generics
• language support for Lists and Maps:
  • List<String> list = [“1”, “2”];
  • list[0]
  • map{“hello”}

not retained in Project coin:

• Elvis operator:
  • use ?: as a shorthand for testing on null
  • conclusion from building a prototype→ doesn't fit well in java
• multiple exception handling
  • disjunctive means of | operator
• properties:
  • changes the type system
  • a lot of work (e.g. reflection api, corner cases …) – the 'enum' specification is demonstrated as a comparable change that involved a lot of rework
  • pseudo-properties workaround: via annotation-processing → Project Lombok
• reified generics
  • source language compatibility issues – java generic erasure was chosen for backward compatibility
  • C# created a separate generic library
  • difficult for other languages to target the a platform with reified generics
• extensible enums
  • most enums are constant
  • low utility

Devoxx 2009: JDK 7 Update

18/11/2009, Mark Reinhold

higlight: Closures in java are BACK!

Aims of JDK7

• modular platform
  • JDK7 status:
    • 13MB download with pack200 compression
    • difficult to support smaller (embedded) hardware
  • → Jigsaw project
    • low-level modules, at the rt.jar level
    • language support: module-info.java file
      • explicit module / version requirements
      • create simpler OS-specific package, with correct dependencies (e.g. deb-packages)
    • OSGi interoperability
• multi-lingual support
  • better JRuby, Jython support on the JVM
  • InvokeDynamic
  • “Da Vinci Machine project”
• productivity enhancement
  • “Project Coin”
  • language changes that improve programming experience. E.g.:
    • type inference with the <> (aka. 'diamond') operator: Map <String,String> m = new <> HashMap();
    • split numbers with '_' for better readability: int a=123_456_789;
    • support binary notation: int b=0b00100100001;
    • Lists: direct construction and access to set/get with []: a[4] = b[5];
    • Map: direct construction and access to set/get with {}: a{“b”}=”xyz”;
    • auto-close Closeable interfaces: try(File f = new File()) where f is always closed correctly.
• performance
  • multi-cores are there! → java support needed.
  • → fork/join framework
  • Dual-Pivot Quicksort
  • Closures: “It's time to add them” – I thought this was dropped from Java7 plans...
    • needed:
      • function literals
      • function types
      • extension methods
    • “doesn't fit in java”:
      • non-local control transfer
      • capture non-final vars
      • library-defined control structures

When?

• Planning shifted
• Milestone 10: 2010/09/09: release candidate