Stream collect list to map

Question

I have this code:

    List<String> list = Arrays.asList("a", "b", "c", "a", "c");
    Map<String, List<String>> map = list.stream().collect(Collectors.groupingBy(
    Function.identity() ,
    Collectors.toCollection(ArrayList::new)
    ));

what it produces is

  {a=[a, a], b=[b], c=[c, c]}

Pretty please how should I write mapping method to get a Map that would give me:

{a=2, b=1, c=2}

You could start by changing `Map> map` to `Map map` - since you don't want a list of `String`(s). — Elliott Frisch, Jul 04 '18 at 15:24

score 3 · Accepted Answer · answered Jul 04 '18 at 15:25

3

Use Collectors.counting

list.stream().collect(Collectors.groupingBy(
            Function.identity(), Collectors.counting()));

The above would give you a Map<String, Long>

answered Jul 04 '18 at 15:25

Thiyagu

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Stream collect list to map

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