2016-08-14から1日間の記事一覧

groupingBy で chunk

grouping by のメモ Map<String, Long> countmap = authors.stream().collect(Collectors.groupingBy(t->t.level, Collectors.counting())); Map<String, List<Author>> mapAuthors = authors.stream().collect(Collectors.groupingBy(t->t.level, Collectors.mapping(u->u, Collectors.toList()</string,></string,>…