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G*Advent Calendar(Groovy,Grails,Gradle,Spock...)Advent Calendar 2016

Day 13
@RyotaMurohoshi(Ryota Murohoshi)

【List】Groovyのコレクション系メソッドチートシート【Object[]】

Last updated at Posted at 2016-12-12

　この投稿は「G*Advent Calendar(Groovy,Grails,Gradle,Spock...) Advent Calendar 2016」の13日目の記事です。

はじめに

　あれ、「Groovyのコレクションのあの操作、なんだっけ？ほらのあの言語でいうあれだよ、あれ？」ってなった時のための一覧性重視のチートシートです。対象クラスは、java.lang.Object[]や、java.utils.Collection、java.utils.Listなど様々です。掲載順は、筆者自身がよく使う順で並べました。副作用があるメソッドは除いてあります。

Groovyコレクション操作、チートシート

// 射影
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].collect { it.length() } == [4, 6, 6, 5, 6]

// 選択
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].findAll { it.contains("#") } == ["C#", "F#"]
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].findAll { it.contains("Clojure") } == []

// 条件を満たす要素が存在するか
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].any { it.contains("#") } == false
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].any { it.contains("#") } == true
assert [].any { it.contains("#") } == false

// すべての要素が条件を満たすか
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].every { it.length() > 3 } == true
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].every { it.length() > 3 } == false
assert [].every { it.contains("#") } == true

// 条件を満たす要素を数え上げ
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].count { it.contains("#") } == 2

// 条件を満たす1要素取得
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].find { it.contains("#") } == null
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].find { it.contains("#") } == "C#"

// ソート
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].sort() == ["Ceylon", "Groovy", "Java", "Kotlin", "Scala"]
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].sort { it.length() } == ["Java", "Scala", "Groovy", "Kotlin", "Ceylon"]

// 射影 + 平滑化
assert [
        ["runtime":".NET", "languages": ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"]],
        ["runtime":"JVM", "languages": ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"]]
    ].collectMany{ it["languages"] } ==
    ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo", "Java", "Groovy", "Kotlin", "Scala", "Ceylon"]

// グループ化
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].groupBy { it.contains("#") ? "has#" : "no#"} ==
    ["has#":["C#", "F#"], "no#":["VB", "IronPython", "IronRuby", "Boo"]]

// 平滑化
assert [["Java", "Groovy", "Kotlin", "Scala", "Ceylon"],  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"]].flatten() ==
    ["Java", "Groovy", "Kotlin", "Scala", "Ceylon", "C#", "F#", "VB", "IronPython", "IronRuby", "Boo"]
assert [[1, 2],[[3, 4], [5,[6]]],[7],[8, 9, 0],[]].flatten() == [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]

// 重複排除
assert [3, 1, 4, 1, 5, 9].toUnique() == [3, 1, 4, 5, 9]

// 重複排除（セットに変換）
assert [3, 1, 4, 1, 5, 9].toSet() == [3, 1, 4, 5, 9] as Set

// 和集合
assert [3, 1, 4, 1, 5, 9].toSet() + [1, 4, 1, 4, 2, 3].toSet() == [3, 1, 4, 1, 5, 9, 2].toSet()

// 共通集合
assert [3, 1, 4, 1, 5, 9].toSet().intersect([1, 4, 1, 4, 2, 3].toSet())  == [1, 4, 3].toSet()

// 差集合
assert [3, 1, 4, 1, 5, 9].toSet() - [1, 4, 1, 4, 2, 3].toSet()  == [5, 9].toSet()

// 順番反転
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].reverse() == ["Ceylon", "Scala", "Kotlin", "Groovy", "Java"]

// 指定要素が存在するか
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].contains("Groovy") == true
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].contains("Groovy") == false

// 要素を指定数ごとにまとめる
assert [1, 2, 3, 4, 5, 6, 7].collate(3) == [[1, 2, 3], [4, 5, 6], [7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, true) == [[1, 2, 3], [4, 5, 6], [7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, false) == [[1, 2, 3], [4, 5, 6]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, 2) == [[1, 2, 3], [3, 4, 5], [5, 6, 7], [7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, 2, true) == [[1, 2, 3], [3, 4, 5], [5, 6, 7], [7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, 2, false) == [[1, 2, 3], [3, 4, 5], [5, 6, 7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, 5) == [[1, 2, 3], [6, 7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, 5, true) == [[1, 2, 3], [6, 7]]
assert [1, 2, 3, 4, 5, 6, 7].collate(3, 5, false) == [[1, 2, 3]]

// 先頭より指定要素数から新たなListを生成
assert  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].take(2) == ["C#", "F#"]

// 末尾より指定要素数から新たなListを生成
assert  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].takeRight(2) == ["IronRuby", "Boo"]

// 先頭より指定条件を満たした要素が続く間の要素から、新たなListを生成
assert  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].takeWhile{ it.contains("#") } == ["C#", "F#"]

// 先頭より指定要素数をのぞいた新たなListを生成
assert  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].drop(2) == ["VB", "IronPython", "IronRuby", "Boo"]

// 末尾より指定要素数をのぞいた新たなListを生成
assert  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].dropRight(2) == ["C#", "F#", "VB", "IronPython"]

// 先頭より指定条件を満たした要素が続く間の要素を取り除いたものから、新たなListを生成
assert  ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].dropWhile{ it.contains("#" )} == ["VB", "IronPython", "IronRuby", "Boo"]

// Map生成
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].collectEntries { [it, it.length()] } ==  [Java:4, Groovy:6, Kotlin:6, Scala:5, Ceylon:6]
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].collectEntries { [it.length(), it] } ==  [4:"Java", 5:"Scala", 6:"Ceylon"]

// 先頭要素
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].first() == "Java"

// 先頭要素
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].head() == "Java"

// 先頭要素以外
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].tail() == ["Groovy", "Kotlin", "Scala", "Ceylon"]

// 末尾要素
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].last() == "Ceylon"

// 末尾要素以外
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].init() == ["Java", "Groovy", "Kotlin", "Scala"]

// 最大要素
assert [3, 1, 4, 1, 5, 9].max() == 9
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].max { it.length() } == "Groovy"

// 最小要素
assert [3, 1, 4, 1, 5, 9].min() == 1
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].min { it.length() } == "Java"

// 合計を求める
assert [3, 1, 4, 1, 5, 9].sum() == 23
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].sum { it.length() } == 27

// グループ分けして要素数え上げ
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].countBy { it.length() } ==  [4:1, 5:1, 6:3]

// インデックス(添え字)（List）
assert ["Android", "iOS", "WindowsPhone"].withIndex() == [["Android", 0], ["iOS", 1], ["WindowsPhone", 2]]

// インデックス(添え字)（Map）
assert ["Android", "iOS", "WindowsPhone"].indexed() == [0: "Android", 1:"iOS", 2:"WindowsPhone"]

// 条件を満たす1要素取得+変換
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].findResult { it.contains("#") ? "${it} has #." : null } == null
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].findResult { it.contains("#") ? "${it} has #." : null } == "C# has #."

// デフォルト値つき条件を満たす1要素取得+変換
assert ["Java", "Groovy", "Kotlin", "Scala", "Ceylon"].findResult("No Result") { it.contains("#") ? "${it} has #." : null } == "No Result"
assert ["C#", "F#", "VB", "IronPython", "IronRuby", "Boo"].findResult("No Result") { it.contains("#") ? "${it} has #." : null } == "C# has #."

リファレンスリンク集

さいごに

　あなたが普段使っているプログラミング言語はなんですか？

　残念ながら自分はGroovyのことは好きなんですが、業務でも趣味でもメインで使ってはいません。普段使いはしませんが、ファイル名を一括で変えるとか、正規表現とかでテキスト処理とか、ウェブAPIのJSONのレスポンスをこね繰り回したりとか、ちょっとしたことをする際にGroovyを使っています。

　そんな時、「あーKotlinのmapってGroovyでなんだっけ？」とか「えーっとC#のWhereはGroovyで、思い出せない。」ってなることがあり、パパッと用途に応じて思い出せるチートシートを作りました！俺得！！！

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