目次 はじめに Collectorを作る Collectorを楽に使う Collectorをまとめる Collectorから生成する はじめに Java 8以降Stream APIはfor文に代わり広く使われる Streamには終端処理がセットになり、その代表がcollectメソッド collectメソッドの引数がjava.util.stream.Collector Collectorを作る // ArrayListに変換するCollector Collector<T, ?, List<T>> toArrayList = Collector.of( ArrayList::new, List::add, (l1, l2) -> { l1.addAll(l2); return l1; }, Characteristics.IDENTITY_FINISH); // 実行 .stream().co
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