Using a Scanner object in a foreach loop

Question

Hi,
I am trying to get this code to work:
String numbers = "45 63 123 4 666";
Scanner scan = new Scanner (numbers);
for (String word : scan)
System.out.println(word);
And I am getting the following error from the compiler:
"foreach not applicable to expression types"
I'm not sure why this is causing a problem. Any enlightenment would be greatly appreciated!
Thanks,
Diane Mega

Answer 1

short answer:
Scanner is not a Collection
Long Answer
the for-each loop is actually an internal java macro which uses an Iterator object to iterate.
and in order to iterate it calls the classes Iterator method and uses that to Iterate across, and the only objects that have iterators are those that implement the Collections interface, and a Scanner is not a collection.
in other words, to use the for-each loop, the object must implement Collection OR it must be a low level array.
the actual macro expansion is equal to
for (type var : coll) {
    body-of-loop
//is the same as
for (Iterator<type> iter = coll.iterator(); iter.hasNext(); ) {
    type var = iter.next();
    body-of-loop
}