On 3/18/2011 10:01 AM, assembling signals wrote:
Hello, community!
I noticed a new error since b134: "Cannot use '<>' with anonymous inner
classes".
The code uses diamond syntax and was error-free before b134.
(Please see reproducible example at the end.)
Can someone explain: is this error even intended?
If so, why this is necessary? If not, is it possible to revert to old behavior?
(BTW: Latest Netbeans even allow to refactor anon-inner-classes to use diamond
syntax.)
Best regards,
Ivan G Shevchenko
As described in the recently published Project Coin documentation for
the developer preview [1], using diamond with anonymous inner class is
specifically disallowed:
It is a compile-time error if a class instance creation expression
declares an anonymous class but uses "<>" in place of a class type
argument list.
It is noted in the document that
(Note that javac in the JDK 7 developer preview erroneously accepts
diamond combined with non-generic classes and accepts some uses of
diamond with anonymous inner classes. These bugs will be corrected in
future builds.)
The future has arrived in b134 :-)
The discussion section of the feature has a brief rationale for this change:
Using diamond with anonymous inner classes is /not/ supported since
doing so in general would require extensions to the class file
signature attribute to represent non-denotable types, a de facto JVM
change.
The public review draft of JSR 334 will have a more in-depth discussion.
Cheers,
-Joe
[1]
http://cr.openjdk.java.net/~darcy/ProjectCoin/ProjectCoin-Documentation-v0.83.html
