Elad Benda Elad Benda - 1 year ago 92
Java Question

who to partition a list by predicate using java8?

I have a list

which i want to split to few small lists.

say all the items that contains with "aaa", all that contains with "bbb" and some more predicates.

How can I do so using java8?

I saw this post but it only splits to 2 lists.

public void partition_list_java8() {

Predicate<String> startWithS = p -> p.toLowerCase().startsWith("s");

Map<Boolean, List<String>> decisionsByS = playerDecisions.stream()


assertTrue(decisionsByS.get(Boolean.TRUE).size() == 3);

I saw this post, but it was very old, before java 8.


You may want to group it in Map of Lists where key will be first character. For instance

List<String> a = Arrays.asList("foo", "Abc", "bar", "baz", "aBc");

Map<Character, List<String>> collect = a.stream()
        .collect(Collectors.groupingBy((String s) -> s.toLowerCase().charAt(0)));



{a=[Abc, aBc], b=[bar, baz], f=[foo]}