RFR(s): 8072726: add adapter to convert Enumeration to Iterator (original) (raw)

Stuart Marks stuart.marks at oracle.com
Sun May 17 00:53:41 UTC 2015

On 5/16/15 3:00 PM, Remi Forax wrote:

Hi Stuart, this change is pretty cool,

Hi Rémi, thanks for looking at this.

In the javadoc of Iterator instead of: Iterable permsIterable = () -> pc.elements().asIterator(); one can write: Iterable permsIterable = pc.elements()::asIterator;

Ah, I carefully tailored that example to capture "pc" instead of the result of calling pc.elements(). With the latter, if iterator() is called a second time, the two Iterator instances will share the same underlying Enumeration and probably interfere with each other. (Maybe I'll add a note to the example explaining that.)

and I wonder if an example with NetworkInterface.getNetworkInterfaces() is not better, I'm not sure a lot of people have to play with permissions outside people of this list.

Yeah I had to look for a long time to find a good example of Enumeration in the JDK libraries. One problem with NetworkInterface.getNetworkInterfaces() is that it's declared to throw SocketException, which is checked, making it clumsy to use within a lambda. There are other possibilities (e.g., getSubInterfaces()) but that's pretty obscure too. Although the permissions stuff is pretty obscure too, they're pretty easy to get, either by getting one from a class' ProtectionDomain, or creating one yourself.

and for the implementation of asIterator, I think the code can be written like this: default Iterator asIterator() { return new Iterator<>() { @Override public boolean hasNext() { return hasMoreElements(); } @Override public E next() { return nextElement(); } }; }

using diamond inference on inner-classes (I think the patch that allows that was integrated) and making calls to Enumeration.this implicit.

Right, I think I wrote my initial prototype before this compiler change went in! Good catch on the Enumeration.this too; I'll make these updates.

s'marks

regards, Rémi On 05/16/2015 02:37 AM, Stuart Marks wrote: Hi all,

Please review this small API enhancement to add a default method "asIterator()" to Enumeration that converts it into an Iterator. Webrev: http://cr.openjdk.java.net/~smarks/reviews/8072726/webrev.0/ Bug: https://bugs.openjdk.java.net/browse/JDK-8072726 Thanks, s'marks

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