Question

I could not find a method in guava that converts a Collection (or Iterator/Iterable) to a Map, something like the following (wildcards omitted for clarity):

public static <T, K, V> Map<K,V> collectionSplitter(Collection<T> source, Function<T,K> kProducer, Function<T,V> vProducer){
    Map<K,V> map = Maps.newHashMap();
    for(T t : source){
        map.put(kProducer.apply(t), vProducer.apply(t));
    }
    return map;
}

Is any existing method that does this? The closest I could find is Splitter.keyValueSplitter(), if T is a String.

Answer 1

The closest I’m aware of is Maps.uniqueIndex – that does the key side, but not the value side… is that close enough?

You could potentially use:

Map<K, V> map = Maps.transformValues(Maps.uniqueIndex(source, kProducer),
                                     vProducer);

Slightly awkward, but it would get the job done, I think…