Idiom for pairwise iteration through a sorted collection

Question

Is there a Java idiom for pairwise iteration through the elements of a sorted Collection? By that I mean that each iteration has access to one element of the co

Answer 1

Write an implementation of Iterator, e.g. (just writing off the top of my head, so code may not work as is)

public class PairwiseIterator implements Iterator> {
    private final Iterator elements;
    private T last;

    public PairwiseIterator(Collection elements) {
        this.elements = elements.iterator();
        last = elements.hasNext() ? elements.next() : null;
    }

    @Override
    public boolean hasNext() {
        return elements.hasNext();
    }

    @Override
    public List next() {
        List result = ImmutableList.of(last, elements.next());
        last = result.get(1);
        return result;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("Remove not allowed with this iterator");
    }

    public static  Iterable> iterable(final Collection elements) {
        return new Iterable() {
            public Iterator iterator() {
                return new PairwiseIterator(elements);
            }
        }
    }
}

I probably don't have the types exactly right, but the 'iterable' method makes it easy to use in foreach constructs:

for(List pair : PairwiseIterator.iterable(orderedSetOfStrings)) {
    // ... do what you need to ...
}