gistfile1.java

public class DeepIterator implements Iterator<Integer> {
	private Stack<Iterator> iteratorStack = new Stack<Iterator>();
	private Integer top = null;

	public DeepIterator(Iterable iterable){
		this.iteratorStack.push(iterable.iterator());
	}

	@Override
	public boolean hasNext() {
		if(this.top != null) return true;

		while(!this.iteratorStack.isEmpty()) {
			Iterator tmpIterator = this.iteratorStack.peek();

			if(tmpIterator.hasNext()){
				Object tmp = tmpIterator.next();
				if(tmp instanceof Integer){
					this.top = (Integer) tmp;
					return true;
				} else if(tmp instanceof Iterable){
					this.iteratorStack.push(((Iterable) tmp).iterator());
				} else {
					throw new RuntimeException("Unsupported data type. ");
				}
			} else {
				this.iteratorStack.pop();
			}
		}
		return false;
	}

	@Override
	public Integer next() throws NoSuchElementException {
		if(hasNext()){
			Integer tmp = this.top;
			this.top = null;
			return tmp;
		}

		throw new NoSuchElementException();
	}

	@Override
	public void remove() {
		throw new UnsupportedOperationException("This is not supported right now.");
	}