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?

Answer 1

It sounds like you should be using Iterators.filter, then checking the value of hasNext on the returned iterator.

Answer 2

Since Guava 7, you can do this using the Iterables.find() overload that takes a default value:

Iterables.find(iterable, predicate, null);

Answer 3

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.

Answer 4

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();
}