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Java8 ラムダ式を変数に代入して再利用する

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ラムダ式はオブジェクトと同じように、変数に代入して再利用ができます。
filter() メソッドを例にして、ラムダ式を変数に代入して再利用してみます。
以下のリストから、8文字以上の文字列のみをフィルタで取り出してみたいと思います。

final List<String> months = 
Arrays.asList("January", "February", "March", "April", "May", "June", "July", "Augast", "September", "October", "November", "December");

final List<String> jewelries = 
Arrays.asList("garnet", "amethyst", "aquamarine", "diamond", "emerald", "pearl", "ruby", "sardonyx", "sapphire", "opal", "topaz", "turquoise");

8文字以上の文字列のみをフィルタするラムダ式を longName 変数に代入します。

final Predicate<String> longName = name -> name.length() >= 8;

以下のように2つの別々のリストの filter() 式に対して、同じ変数(longName)に代入したラムダ式を適用しています。

// フィルタして出力する
final List<String> longNameMonths = months.stream().filter(longName).collect(Collectors.toList());
final List<String> longNameJewelries = jewelries.stream().filter(longName).collect(Collectors.toList());

longNameMonths.forEach(System.out::println);
longNameJewelries.forEach(System.out::println);

結果、以下のように8文字以上の文字列のみが出力されました。

February
September
November
December
amethyst
aquamarine
sardonyx
sapphire
turquoise
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