Re: 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 
<jbluettdun...@gmail.com <mailto:jbluettdun...@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
    <dbros...@mebigfatguy.com <mailto:dbros...@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);            
        }         }     } }