Make iterators cloneable?

[Dave Brosius]

Yes Louis is correct.

I want the pair wise associations or all elements of a set.

Fee-Fi

Fee-Fo

Fee-Fum

Fi-Fo

Fi-Fum

Fo-Fum


the independent iterators produce Fee-Fee (etc) as well as the duplicate 
Fee-Fi and Fi-Fee (etc), both of which i don't want.


This is obviously simplistic with index based collections, but not with 
sets/maps

I don't see why an Iterator isn't by nature easily cloneable.



On 09/10/2016 06:45 PM, Jonathan Bluett-Duncan wrote:
> Ah okay Louis, if that's the case then that certainly makes sense, and 
> I'd agree that there's no good way of doing so, as one would need to 
> copy the set into a list.
>
> Dave, did Louis hit the mark? If not, would you kindly go into further 
> detail as to exactly what it is you're trying to do?
>
> Best,
> Jonathan
>
> On 10 September 2016 at 23:36, Jonathan Bluett-Duncan 
> <jbluettduncan at gmail.com <mailto:jbluettduncan at gmail.com>> wrote:
>
>     Hi Dave,
>
>     Rather than using Iterator.clone(), how about you just call
>     collection.iterator() 2 times to return 2 unique, non-same
>     iterators; something like the following:
>
>     import java.util.Collections;
>     import java.util.Iterator;
>     import java.util.Set;
>     import java.util.concurrent.ConcurrentHashMap;
>
>     public class Example {public static void main(String[] args) { Set<String> s =
>     Collections.newSetFromMap(new ConcurrentHashMap<String,
>     Boolean>()); s.add("Fee"); s.add("Fi"); s.add("Fo"); s.add("Fum");
>     Iterator<String> it1 = s.iterator();      for (String v1 =null; it1.hasNext(); v1 =it1.next()) {
>            Iterator<String> it2 = s.iterator();// a completely separate iterator to it1 for (String v2 =null; it2.hasNext(); v2 = it2.next()) {System.out.println(v1 + " <-->" + v2); } } } }
>
>     Or, even better, if you're using Java 5+, you can skip using
>     Iterators altogether and use for-loops directly:
>
>     import java.util.Collections;
>     import java.util.Set;
>     import java.util.concurrent.ConcurrentHashMap;
>
>     public class Example {public static void main(String[] args) { Set<String> s =
>     Collections.newSetFromMap(new ConcurrentHashMap<String,
>     Boolean>()); s.add("Fee"); s.add("Fi"); s.add("Fo"); s.add("Fum");      for (String v1 : s) {
>            for (String v2 : s) {System.out.println(v1 + "<-->" + v2); } } } }
>
>     Kind regards,
>     Jonathan
>     On 10 September 2016 at 23:13, Dave Brosius
>     <dbrosius at mebigfatguy.com <mailto:dbrosius at mebigfatguy.com>> wrote:
>
>         It would be nice to be able to associate each element in a
>         collection with another element in the collection, which is
>         something very easily done with index based collections, but
>         with sets, etc this isn't so easy... unless i'm having a
>         brainfart. So i'd like to do this, but Iterator doesn't
>         implement Cloneable... Any reason not to? or is there another
>         way that's missing me? public class ItClone {     public
>         static void main(String[] args) {         Set<String> s =
>         Collections.newSetFromMap(new ConcurrentHashMap<String,
>         Boolean>());         s.add("Fee");         s.add("Fi");      
>           s.add("Fo");         s.add("Fum");         Iterator<String>
>         it1 = s.iterator();         while (it1.hasNext()) {          
>           String v1 = it1.next();             Iterator<String> it2 =
>         (Iterator<String>) it1.*clone*();             while
>         (it2.hasNext()) {                 String v2 = it2.next();    
>                     System.out.println(v1 + " <-->" + v2);            
>         }         }     } } 
>