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
2.3k
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
310
hpc170_slide.pdf
serihiro
0
64
画像解像度別ImageNetの100 iterationの合計処理時間比較
serihiro
0
110
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
61
Introduction to Parallel Computing 2.2
serihiro
0
60
My summer internship result at Treasure Data 2018 #td_intern
serihiro
0
2.1k
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
Creating Awesome Change in SmartNews! En
martin_lover
0
110
監視 やばい
syossan27
12
10k
プロダクトエンジニアのしごと 〜 受託 × 高難度を乗り越えるOptium開発 〜
algoartis
0
160
Bedrock×MCPで社内ブログ執筆文化を育てたい!
har1101
7
1.4k
Contribute to Comunities | React Tokyo Meetup #4 LT
sasagar
0
590
UMAPをざっくりと理解 / Overview of UMAP
kaityo256
PRO
3
1.4k
ASP.NETアプリケーションのモダナイゼーションについて
tomokusaba
0
240
読書シェア会 vol.4 『ダイナミックリチーミング 第2版』
kotaro666
0
110
Flutterでllama.cppをつかってローカルLLMを試してみた
sakuraidayo
0
120
Boost Your Performance and Developer Productivity with Jakarta EE 11
ivargrimstad
0
760
大LLM時代にこの先生きのこるには-ITエンジニア編
fumiyakume
8
3.3k
音声プラットフォームのアーキテクチャ変遷から学ぶ、クラウドネイティブなバッチ処理 (20250422_CNDS2025_Batch_Architecture)
thousanda
0
380
Featured
See All Featured
RailsConf 2023
tenderlove
30
1.1k
The Web Performance Landscape in 2024 [PerfNow 2024]
tammyeverts
5
550
It's Worth the Effort
3n
184
28k
Rails Girls Zürich Keynote
gr2m
94
13k
Build The Right Thing And Hit Your Dates
maggiecrowley
35
2.7k
Facilitating Awesome Meetings
lara
54
6.3k
Principles of Awesome APIs and How to Build Them.
keavy
126
17k
Mobile First: as difficult as doing things right
swwweet
223
9.6k
Scaling GitHub
holman
459
140k
GraphQLとの向き合い方2022年版
quramy
46
14k
Faster Mobile Websites
deanohume
306
31k
個人開発の失敗を避けるイケてる考え方 / tips for indie hackers
panda_program
105
19k
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