Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
5分で分かるかもしれないjava8 Stream API
Search
Kazuhiro Serizawa
November 26, 2015
Programming
1
2.2k
5分で分かるかもしれないjava8 Stream API
Kazuhiro Serizawa
November 26, 2015
Tweet
Share
More Decks by Kazuhiro Serizawa
See All by Kazuhiro Serizawa
Accelerating Machine Learning I/O by Overlapping Data Staging and Mini-batch Generations
serihiro
1
290
hpc170_slide.pdf
serihiro
0
52
画像解像度別ImageNetの100 iterationの合計処理時間比較
serihiro
0
100
深層ニューラルネットワークにおける訓練高速化のための自動最適化
serihiro
0
49
Introduction to Parallel Computing 2.2
serihiro
0
54
My summer internship result at Treasure Data 2018 #td_intern
serihiro
0
2k
startupでもrails使うなら これだけはやっとけ的 tips集
serihiro
19
10k
つらくないコードレビューの運用
serihiro
43
20k
Other Decks in Programming
See All in Programming
Linux && Docker 研修/Linux && Docker training
forrep
24
4.5k
Honoのおもしろいミドルウェアをみてみよう
yusukebe
1
210
Amazon Q Developer Proで効率化するAPI開発入門
seike460
PRO
0
110
PHPカンファレンス名古屋2025 タスク分解の試行錯誤〜レビュー負荷を下げるために〜
soichi
1
200
Introduction to kotlinx.rpc
arawn
0
700
Lottieアニメーションをカスタマイズしてみた
tahia910
0
130
ファインディLT_ポケモン対戦の定量的分析
fufufukakaka
0
710
プログラミング言語学習のススメ / why-do-i-learn-programming-language
yashi8484
0
130
ソフトウェアエンジニアの成長
masuda220
PRO
10
1.1k
Immutable ActiveRecord
megane42
0
140
Flutter × Firebase Genkit で加速する生成 AI アプリ開発
coborinai
0
160
2,500万ユーザーを支えるSREチームの6年間のスクラムのカイゼン
honmarkhunt
6
5.3k
Featured
See All Featured
Easily Structure & Communicate Ideas using Wireframe
afnizarnur
193
16k
The Straight Up "How To Draw Better" Workshop
denniskardys
232
140k
Learning to Love Humans: Emotional Interface Design
aarron
273
40k
Unsuck your backbone
ammeep
669
57k
Refactoring Trust on Your Teams (GOTO; Chicago 2020)
rmw
33
2.8k
VelocityConf: Rendering Performance Case Studies
addyosmani
328
24k
Thoughts on Productivity
jonyablonski
69
4.5k
A Philosophy of Restraint
colly
203
16k
How GitHub (no longer) Works
holman
314
140k
Music & Morning Musume
bryan
46
6.3k
Understanding Cognitive Biases in Performance Measurement
bluesmoon
27
1.6k
[RailsConf 2023] Rails as a piece of cake
palkan
53
5.2k
Transcript
5Ͱ͔Δ͔͠Εͳ͍ java8 Stream API
java8ʹ͍ͭͯ • 20143݄18ʹOracle͔Βެ։ • “ੈքҰͷ։ൃϓϥοτϑΥʔϜͷըظతͳϦϦʔ ε” ※OracleେຊӦൃද • ϥϜμࣜɺStreamAPIɺDate and
Time APIͳͲͷ ৽ػೳͷಋೖͰjavaքʹֵ໋͕ʂ ʢͱࢥ͚ͬͨͲͦ͜·ͰΓ্͕Βͳ͔ͬͨʣ
ࠓ͔̑͠ͳ͍ͷͰ • Stream APIʹ͍ͭͯ֓ཁΛ͠·͢ • ʮjavaগ͠ϚγʹͳͬͨΑ͏ͩͳʯ ͱ͍͏ͷΛײ͡औͬͯΒ͑Ε͍Ͱ͢
Stream APIͱʁ • ྻɺϦετͳͲͷෳͷσʔλʹ͓͚Δू ૢ࡞ͷαϙʔτΛߦ͏API • ฒߦॲཧΒͷϕϯϦػೳΛఏڙͯ͘͠ΕΔ UtilͰͳ͘Interface͚ͩΛఏڙ͢Δ
Stream APIͱʁ • ཁ͢ΔʹRubyͰݴ͏ͱ͜Ζͷ • Enumerable#each • Enumerable#select • Enumerable#map
• ͜ΕΒͷॲཧΛʮܾ·ͬͨखॱͰ࣮ߦ͢ΔʯAPI • Stream API ≠࣮ɻInterfaceͷΈΛఆ͍ٛͯ͠Δɻ
StreamΛΘͳ͍߹ͷྫ List<Integer> list = Arrays.asList(1,2,3); Integer result = 0; for
(Integer i : list) { result += i * i; } System.out.println(result); //14
ͳ͓ruby result = [1,2,3] .map{ |i| i*i } .inject{ |a,b|
a + b } puts result #=> 14
StreamΛ͏߹ͷྫ List<Integer> list = Arrays.asList(1,2,3); Integer result = list.stream() .map(x
-> x * x) .reduce((a, b) -> a + b) .get(); System.out.println(result); //14
Stream APIΛ༻͍࣮ͨ "SSBZ -JTUͳͲͷ %BUBTPVSDF TUSFBN࡞ தؒૢ࡞ ϑΟϧλϦϯάɾͷૢ࡞ͳͲ ऴૢ࡞ ूૢ࡞ɾผΫϥεͷมɾ
ஞ࣍ॲཧͳͲ ॲཧ͞Εͨ݁Ռ list.stream() .map(x -> x * x) .reduce((a, b) -> a + b) .get();
ඪ४ϥΠϒϥϦ with Stream Stream<String> lines = Files.lines(path) lines.filter(line -> line.startsWith(“a”))
.map(s -> s.toUpperCase) .forEach(s -> System.out.println(s)); // “AMAZON” // “ATOM”
StreamʹΑͬͯԿ͕͏Ε͍͔͠ • σʔλϦιʔεૢ࡞ͷ࣮ͷ؆ུԽ • ϥϜμࣜͱΈ߹ΘͤΔ͜ͱͰ ؔܕͬΆ͍syntaxʹ • σʔλϦιʔεʹର͢Δฒߦॲཧɾࢄॲཧ Λstream()ϝιουʹӅṭԽ࣮ͯ͠Ͱ͖Δ
Collection frameworkͩͱ ϚϧνεϨουͰฒߦॲཧ͢ΔstreamΛ࡞ΕΔ List<Integer> list = Arrays.asList(1,2,3); Integer result =
list.parallelStream() .map(x -> x * x) .reduce((a, b) -> a + b) .get(); System.out.println(result); //14
༨ஊɿ Apache SparkΛͬͨࢄॲཧ࣮ input. flatMap(line -> Arrays.asList(line.split("\\s+"))) .mapToPair(word -> new
Tuple2(word, 1)) .reduceByKey((x, y) -> (Integer) x + (Integer) y) .sortByKey() .collect();
Stream APIͷ·ͱΊ • ීஈྑ͘͏Collection Frameworkͷॲཧ͕ γϯϓϧʹ࣮Ͱ͖ΔΑ͏ʹͳΔ • rubyʹ༏͍͠ • ࢄɾฒߦॲཧΛӅṭԽ࣮ͯ͠Ͱ͖ͦ͏ͳ
ઃܭํΛ͍ࣔͯ͠Δ