Iterables.find and Iterators.find - instead of throwing exception, get null
Question
I'm using google-collections and trying to find the first element that satisfies Predicate if not, return me 'null'.
Unfortunately, Iterables.find and Iterators.find throws NoSuchElementException when no element is found.
Now, I am forced to do
Object found = null;
if ( Iterators.any( newIterator(...) , my_predicate )
{
found = Iterators.find( newIterator(...), my_predicate )
}
I can surround by 'try/catch' and do the same thing but for my use-cases, I am going to encounter many cases where no-element is found.
Is there a simpler way of doing this?
Solution
It sounds like you should be using Iterators.filter, then checking the value of hasNext on the returned iterator.
OTHER TIPS
Since Guava 7, you can do this using the Iterables.find() overload that takes a default value:
Iterables.find(iterable, predicate, null);
This was filed as a feature request:
http://code.google.com/p/guava-libraries/issues/detail?id=217
We are actually in progress on it.
I'm not sure if this qualifies as simpler, but at least it avoids exceptions and requires only one pass over the source iterable:
public static <T> T findMatchOrNull(Iterator<T> source, Predicate<T> pred) {
Iterator<T> matching = Iterators.filter(source, pred);
Iterator<T> padded = Iterators.concat(matching, Iterators.<T>singletonIterator(null));
return padded.next();
}