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Collectors.joiningCollectors.groupingByStream
分類器で要素をグループ化するCollectorを返します。
문법
Collectors.groupingBy(classifier)예제
아래 값을 입력하면 예제에 즉시 반영됩니다.
List→String→words→of→Map→Character→grouped→stream→collect→Collectors→groupingBy→charAt→System→out→println→apple→ant→banana→cherry→cat→List<String> words = List.of("apple","ant","banana","cherry","cat");
Map<Character, List<String>> grouped = words.stream()
.collect(Collectors.groupingBy(w -> w.charAt(0)));
System.out.println(grouped);
// {a=[apple, ant], b=[banana], c=[cherry, cat]}