RFR: 8005051: default methods for Iterator (original) (raw)

Remi Forax forax at univ-mlv.fr
Fri Dec 14 10:54:51 UTC 2012

Hi Akhil,

On 12/14/2012 02:24 AM, Akhil Arora wrote:

As part of the library lambdafication, this patch adds a forEach default method to Iterator, and converts remove() into a default method so that implementations of Iterator no longer have to override remove if they desire the default behavior, which is to throw an UnsupportedOperationException.

http://cr.openjdk.java.net/~akhil/8005051.0/webrev/ The above patch requires a small patch to an internal class which happens to implement both Iterable and Iterator. Now both Iterable and Iterator supply a default forEach method, so the compiler balks. One minimally intrusive solution is for this class to override both defaults and provide its own version of forEach. http://cr.openjdk.java.net/~akhil/8005053.0/webrev/

The issue here is in the code of ASM wich is an external library imported in the JDK, so not sure it's a good idea to patch it.

Moreover, goggling for "implement Iterable, Iterator" shows that this anti-pattern is used too frequently to not step back and see if a better solution is not possible. https://encrypted.google.com/search?hl=en&q=%22implements+Iterable%3C*%3E%2C+Iterator%3C*%3E%22

We can't remove Collection.forEach without having perf issue because the stream pipeline use it. Iterator.forEach can be removed but it's a pity because it's really convenient, a possble solution is to rename Iterator.forEach() to something else.

Please review Thanks

cheers, Rémi

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