How can I make an iterator that never ends?

Question

I was just wondering what the easiest way to iterate over a set indefinitely, i.e. when it reaches the end it next(); calls the first object. I'm assuming that this is not an already predefined function in Java, so just looking for the easiest way to implement this in Java.

Answer 1

How about ?

List<String> list = // ArraysList
Interator<String> it = null;

while(true) {
 it = list.iterator();
 while(it.hasNext()) {
   System.out.println(it.next());
 }
}

Answer 2

If you don't want to use Guava but still want a reusable solution:

public static class CyclicIterator<E, C extends Collection<E>> implements Iterator<E> {
    final private C mElements;
    private Iterator<E> mIterator;

    public CyclicIterator(C elements) {
        mElements = elements;
        mIterator = elements.iterator();
    }

    @Override
    public boolean hasNext() {
        if (! mIterator.hasNext()) {
            mIterator = mElements.iterator();
        }
        return mIterator.hasNext();
    }

    @Override
    public E next() {
        if (! mIterator.hasNext()) {
            mIterator = mElements.iterator();
        }
        return mIterator.next();
    }
}

Note: this doesn't support the remove() method but it could easily be added if needed. Also it's not thread safe.