ImmutableMap collector for Stream of Map.Entry

[will-molloy]

Noticed a lot of code looks like this:

    ImmutableMap<Integer, String> map = Stream.of(1, 2, 3, 4, 5)
        .map(i -> Maps.immutableEntry(i, String.valueOf(i)))
        .collect(toImmutableMap(Map.Entry::getKey, Map.Entry::getValue));

Would be nice if there was a collector for collecting Stream<Map.Entry<K, V>> into ImmutableMap<K, V> so the above can look like:

    ImmutableMap<Integer, String> map = Stream.of(1, 2, 3, 4, 5)
        .map(i -> Maps.immutableEntry(i, String.valueOf(i)))
        .collect(toImmutableMap());

---

The collector can be implemented like:

  static <K, V> Collector<Map.Entry<K, V>, ?, ImmutableMap<K, V>> toImmutableMap() {
    return ImmutableMap.toImmutableMap(Map.Entry::getKey, Map.Entry::getValue);
  }

[perceptron8]

Isn't

ImmutableMap<Integer, String> map = Stream.of(1, 2, 3, 4, 5)
	.collect(toImmutableMap(i -> i, String::valueOf));

even nicer? ;)

[perceptron8]

Also, this issue seems to be related to #2632.

[will-molloy]

Lol sorry my example wasn't very good.

Usually the Stream<Map.Entry> is created from entrySet().stream().

Also have seen it with flatmap. E.g.

    ImmutableMap<String, Integer> map =
        Stream.of(1, 2, 3)
            .flatMap(i -> Stream.of("A", "B", "C").map(s -> Maps.immutableEntry(s + i, i)))
            .collect(toImmutableMap(Map.Entry::getKey, Map.Entry::getValue));

Have also seen streams of Table.Cell with

.collect(toImmutableTable(Table.Cell::getRowKey, Table.Cell::getColumnKey, Table.Cell::getValue));