DevoxxUK Lambdas Lab (original) (raw)

Brian Goetz brian.goetz at oracle.com
Wed Apr 3 05:31:34 PDT 2013

ACTION: Add a static method to Map.Entry: public static <K, V> Entry<K, V> of(K key, V value) { return new AbstractMap.SimpleImmutableEntry<K, V>(key, value); }

Been down this rathole, and we retreated. While you can make a stream out of Map.Entry, doing anything more than simple filtering and forEaching is unlikely to result in a happy outcome. If it hurts, don't do it.

ACTION: Add a much better way to convert a stream of Entry to a Map. Perhaps: .collect(Collectors.toMap(entry -> getKey(), entry -> entry.getValue()));

Or better yet, don't encourage people to make streams of Map.Entry.

ACTION: Can there be some kind of reducingSum() method? It feels like a common use case, and might provide the source code for people to look at providing the example code for them to then learn and write more advanced reducers themselves.

Do you mean something like:

Collector<T, Integer> counting() { return reducing((T t) -> 1, Integer::sum); }

?

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