/**
* Obtain the contents of the current node.
*
* @timing O(1)
* @precond itemExists()
*/
public I item() throws NoCurrentItem280Exception {
if (!itemExists()) throw new NoCurrentItem280Exception("A current item must exist");
return cur.item();
}
/**
* Advance to the root of the ith subtree.
*
* @timing O(1)
* @param i subtree to advance to
*/
public void goSubtree(int i) {
parent = cur;
index = i;
cur = cur.subnode(i);
}