[OpenJDK 2D-Dev] 2D-related types that are candidates to be FunctionalInterfaces in JDK 8

[Phil Race]

Joe,

|What were the criteria used to identify candidates?
It looks like its finding a public API interface with a
single abstract method.

|My sense is that many of the ones identified are not ones
that would be appropriate for lambda expressions.

The pattern that would seem most useful is where the application
will need to iterate over a collection of these in parallel, is that 
correct ?
Some, like Printable, could not be properly used like that.
Maybe some of the listeners/observers might match the pattern
that there could be multiple of these that might need to be notified
but in reality there will usually be zero, sometimes one.

Perhaps the most likely candidate I see is ServiceRegistry.Filter|||.
|
BTW The decoder ring is here :- http://openjdk.java.net/groups/2d/
under "Regarding Java 2D's source code".
and there's a link there to additional info here :
http://openjdk.java.net/groups/2d/2dawtfiles.html

-phil.


On 2/8/2013 4:11 PM, Joseph Darcy wrote:
> Hello,
>
> As part of Project Lambda, a FunctionalInterface annotation type was 
> added to the platform to mark interfaces that are intended to be used 
> in lambda expressions.  I've sent out a code review request to add 
> this annotation to types in the core-libs area [1] and have just 
> pushed the changeset into TL [2].
>
> To assist the 2D team in adding analogous annotations to your types, 
> the list of candidate types in for 2D-related classes in java.* and 
> javax.* is given below.  I recommend sub-tasks of JDK-8005297 "Add 
> FunctionalInterface support to the platform" be used to track the work 
> of adding @FunctionalInterface annotations to 2D types
>
> In terms of how the annotation should be used, the benefit of the 
> annotation is that is clearly documents the type is intended to be 
> used for lambda expressions and is unlikely to evolve such that is 
> cannot be used with lambda expressions.
>
> To a first approximation, if a candidate type today is commonly 
> created using anonymous inner classes, it is reasonable to add the 
> functionalInterface annotation.  Note that the compiler will allow any 
> type meeting the structural requirements of a functional interface to be
> used in a lambda expression; the annotation just provides 
> documentation of intent.
>
> Having misplaced my 2D vs AWT vs Swing decoder ring, consideration of 
> these 2D types was previously sent to other aliases [3] [4].

>
> Thanks,
>
> -Joe
>
> [1] 
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2013-February/014292.html 
>
>
> [2] http://hg.openjdk.java.net/jdk8/tl/jdk/rev/522fb3867a3a
>
> [3] 
> http://mail.openjdk.java.net/pipermail/awt-dev/2013-February/004213.html
>
> [4] 
> http://mail.openjdk.java.net/pipermail/swing-dev/2013-February/002535.html
>
> -=-=-=-=-
>
> jdk/src/share/classes/java/awt/Stroke.java:58: Note: Candidate 
> functional interface
> public interface Stroke {
>        ^
>
> jdk/src/share/classes/java/awt/image/TileObserver.java:39: Note: 
> Candidate functional interface
> public interface TileObserver {
>
> jdk/src/share/classes/java/awt/image/ImageObserver.java:40: Note: 
> Candidate functional interface
> public interface ImageObserver {
>        ^
> jdk/src/share/classes/java/awt/image/renderable/RenderedImageFactory.java:47: 
> Note: Candidate functional interface
> public interface RenderedImageFactory {
>        ^
> jdk/src/share/classes/java/awt/image/TileObserver.java:39: Note: 
> Candidate functional interface
> public interface TileObserver {
>
> jdk/src/share/classes/java/awt/print/Printable.java:105: Note: 
> Candidate functional interface
> public interface Printable {
>        ^
> jdk/src/share/classes/java/awt/PrintGraphics.java:33: Note: Candidate 
> functional interface
> public interface PrintGraphics {
>        ^
> jdk/src/share/classes/javax/print/FlavorException.java:39: Note: 
> Candidate functional interface
> public interface FlavorException {
>        ^
> jdk/src/share/classes/javax/print/event/PrintServiceAttributeListener.java:37: 
> Note: Candidate functional interface
> public interface PrintServiceAttributeListener {
>        ^
> jdk/src/share/classes/javax/print/event/PrintJobAttributeListener.java:34: 
> Note: Candidate functional interface
> public interface PrintJobAttributeListener {
>        ^
> jdk/src/share/classes/javax/imageio/IIOParamController.java:99: Note: 
> Candidate functional interface
> public interface IIOParamController {
>        ^
> jdk/src/share/classes/javax/imageio/event/IIOWriteWarningListener.java:46: 
> Note: Candidate functional interface
> public interface IIOWriteWarningListener extends EventListener {
>        ^
> jdk/src/share/classes/javax/imageio/event/IIOReadWarningListener.java:46: 
> Note: Candidate functional interface
> public interface IIOReadWarningListener extends EventListener {
>        ^
> jdk/src/share/classes/javax/imageio/metadata/IIOMetadataController.java:67: 
> Note: Candidate functional interface
> public interface IIOMetadataController {
>        ^
> jdk/src/share/classes/javax/imageio/spi/ServiceRegistry.java:464: 
> Note: Candidate functional interface
>     public interface Filter {
>
>