ARM API Support

[Joe Darcy]

Rémi Forax wrote:
> Le 24/06/2010 02:08, Joe Darcy a écrit :
>   
>> Greetings
>>
>> The initial API changes to support the Project Coin feature automatic
>> resource management (ARM) blocks have been pushed into JDK 7 [1] and
>> will appear in subsequent builds. The corresponding compiler changes to
>> support the actual language feature remain in progress.
>>
>> The initial API work to support ARM was divided into two pieces,
>> essential API support and retrofitting platform classes. The essential
>> support includes:
>>
>> * A new interface java.lang.AutoCloseable which defines a single method
>>    void close() throws Exception
>>
>> * A new enum constant in the language model:
>>    javax.lang.model.element.ElementKind.RESOURCE_VARIABLE
>>
>> * Methods on java.lang.Throwable to add and retrieve information about
>> suppressed exceptions, including printing out suppressed exceptions in
>> stack traces.
>>
>> The retrofitting includes:
>>
>> * Having java.io.Closeable extend java.lang.AutoCloseable. (From a
>> typing perspective, a subtype of AutoCloseable can be declared to throw
>> fewer exceptions than the supertype. Therefore is is fine for the close
>> method in AutoCloseable to throw Exception and the close method in
>> Closeable to throw the more specific IOException. It would even be fine
>> for the close method in a subtype of AutoCloseable to be declared to
>> throw no exceptions at all.)
>>
>> * Adding a close method to java.nio.channels.FileLock and having
>> FileLock implement AutoCloseable.
>>
>> * Adding Closeable as an interface implemented by
>> javax.imageio.stream.ImageInputStream.
>>
>> Other platform classes may be retrofitted to implement AutoCloseable or
>> Closable in future builds.
>>
>> Compared to the API support in earlier versions of the ARM proposal, the
>> top-level interface to mark participation in ARM is in package java.lang
>> rather than its own package and, after consultation with the JDBC and
>> graphics teams, neither java.sql.* nor java.awt.Graphics were
>> retrofitted for ARM.
>>
>> -Joe
>>
>> [1] http://hg.openjdk.java.net/jdk7/tl/jdk/rev/c4d60bcce958
>>      http://hg.openjdk.java.net/jdk7/tl/langtools/rev/be5cafeb318d
>>    
>>     
>
> There is a bug in printStackTrace(PrintStreamOrWriter)
>
> Set<Throwable> dejaVu = new HashSet<Throwable>();
> should be:
> Set<Throwable> dejaVu = Collections.newSetFromMap(
> new IdentityHashMap<Throwable,Boolean>());
>
> The current code doesn't work as expected if an exception overrides 
> Throwable.equals.
>   

Hi Rémi,

Thanks for catching this bug.  I'll correct that when I next edit the 
file -- I plan to change the addSuppressedException method to throw an 
exception if the exception tries to suppress itself.

-Joe