/**
* Get no more than one item that matches the given query in the context of this object.
*
* @param query the query to match
* @param params
* @return the item that matches this query, or <code>Item.NULL</code> if none
*/
public Item optional(String query, Object... params) {
ItemList result = executeQuery(query, ZERO_OR_ONE, params);
assert result.size() <= 1 : "expected zero or one results, got " + result.size();
return result.size() == 0 ? Item.NULL : result.get(0);
}
/**
* Get the one and only item that matches the given query in the context of this object.
*
* @param query the query to match
* @param params
* @return the unique item that matches the query
*/
public Item single(String query, Object... params) {
ItemList result = executeQuery(query, EXACTLY_ONE, params);
assert result.size() == 1 : "expected single result, got " + result.size();
return result.get(0);
}