Collection to Iterable

Question

How can I get a java.lang.Iterable from a collection like a Set or a List? Thanks!

Do you mean `Iterator` instead of `Iterable`? A `List` implements the `Iterable` interface. An `Iterator` allows you to iterate through a `List`'s elements. — nwinkler, Mar 16 '12 at 16:21

score 100 · Accepted Answer · edited Jun 26 '20 at 20:26

100

A Collection is an Iterable.

So you can write:

public static void main(String args[]) {
    List<String> list = new ArrayList<String>();
    list.add("a string");

    Iterable<String> iterable = list;
    for (String s : iterable) {
        System.out.println(s);
    }
}

edited Jun 26 '20 at 20:26

Basil Bourque

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answered Mar 16 '12 at 16:19

assylias

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I know that the OP asked about it, but the assignment to `Iterable` is entirely unnecessary. – nwinkler Mar 16 '12 at 16:28
1

@nwinkler agreed with your comment. – assylias Mar 16 '12 at 16:30
1

@myborobudur : what was the issue you had with the generics ? – Newtopian Aug 15 '16 at 17:51

score 12 · Answer 2 · edited Sep 17 '16 at 05:38

12

It's not clear to me what you need, so:

this gets you an Iterator

SortedSet<String> sortedSet = new TreeSet<String>();
Iterator<String> iterator = sortedSet.iterator();

Sets and Lists are Iterables, that's why you can do the following:

SortedSet<String> sortedSet = new TreeSet<String>();
Iterable<String> iterable = (Iterable<String>)sortedSet;

edited Sep 17 '16 at 05:38

shujin

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answered Mar 16 '12 at 16:20

Tom

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The OP asks for `Iterable` not an `Iterator` – amit Mar 16 '12 at 16:21

score 7 · Answer 3 · answered Mar 16 '12 at 16:21

7

Iterable is a super interface to Collection, so any class (such as Set or List) that implements Collection also implements Iterable.

answered Mar 16 '12 at 16:21

highlycaffeinated

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score 2 · Answer 4 · answered Mar 16 '12 at 16:22

2

Both Set and List interfaces extend the Collection interface, which itself extends the Iterable interface.

answered Mar 16 '12 at 16:22

raveturned

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Nathan Hughes · Answer 5 · 2012-03-16T18:01:47.117

java.util.Collection extends java.lang.Iterable, you don't have to do anything, it already is an Iterable.

groovy:000> mylist = [1,2,3]
===> [1, 2, 3]
groovy:000> mylist.class
===> class java.util.ArrayList
groovy:000> mylist instanceof Iterable
===> true
groovy:000> def doStuffWithIterable(Iterable i) {
groovy:001>   def iterator = i.iterator()
groovy:002>   while (iterator.hasNext()) {
groovy:003>     println iterator.next()
groovy:004>   }
groovy:005> }
===> true
groovy:000> doStuffWithIterable(mylist)
1
2
3
===> null

Collection to Iterable

5 Answers5