Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 45 views

    Streams API: Java SE

    Uploaded by

    sissthwae oo
    The document discusses Java Streams API. It defines a Stream as a sequence of elements supporting sequential and parallel aggregate operations. Streams are lazy collections that allow chaining operations such as filtering, mapping, matching, reducing, and collecting. The key benefits of Streams include internal iteration, support for sequential and parallel processing, and intermediate operations that enable pipelines of transformations. Common stream operations include creation from collections, files and ranges, intermediate operations like filter, map and flatMap, and terminal operations like forEach, count and reduce.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Streams API: Java SE

    Uploaded by

    sissthwae oo
    45 views25 pages
    The document discusses Java Streams API. It defines a Stream as a sequence of elements supporting sequential and parallel aggregate operations. Streams are lazy collections that allow chaining operations such as filtering, mapping, matching, reducing, and collecting. The key benefits of Streams include internal iteration, support for sequential and parallel processing, and intermediate operations that enable pipelines of transformations. Common stream operations include creation from collections, files and ranges, intermediate operations like filter, map and flatMap, and terminal operations like forEach, count and reduce.

    Original Description:

    Original Title

    19.Streams

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    The document discusses Java Streams API. It defines a Stream as a sequence of elements supporting sequential and parallel aggregate operations. Streams are lazy collections that allow chaining operations such as filtering, mapping, matching, reducing, and collecting. The key benefits of Streams include internal iteration, support for sequential and parallel processing, and intermediate operations that enable pipelines of transformations. Common stream operations include creation from collections, files and ranges, intermediate operations like filter, map and flatMap, and terminal operations like forEach, count and reduce.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    45 views25 pages

    Streams API: Java SE

    Uploaded by

    sissthwae oo
    The document discusses Java Streams API. It defines a Stream as a sequence of elements supporting sequential and parallel aggregate operations. Streams are lazy collections that allow chaining operations such as filtering, mapping, matching, reducing, and collecting. The key benefits of Streams include internal iteration, support for sequential and parallel processing, and intermediate operations that enable pipelines of transformations. Common stream operations include creation from collections, files and ranges, intermediate operations like filter, map and flatMap, and terminal operations like forEach, count and reduce.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 25

    Streams API

    Java SE
    Contents

    • Overview

    • What is a Streams?

    • Stream Operations

    • Sequential & Parallel Streams


    Overview
    • Java SE 8 မတiuင&မ'(က၊ collection တစ&ခuအတ.င:& /i data မ01:အ1:
    parallel processing 2ပuလuပ&လiueသ1 အခ8၊ for ဒ8မ'မဟuတ& while
    iteration အ1:အသu;:2ပuက1 2ပင&ပမ' Control လuပ&<ကရ၏

    • External Iteration လuပ&2ခင&?သည& parallel processing အ1?


    eဆ1င&B.က&ရန& ခက&ခDeစပ8သည&

    • Stream API သည& Internal Iteration အ1?ပ;Eပiu?eပ?Fပ(?၊


    sequential eက1 parallel processing ပ8 လuပ&eဆ1င&eစGiuင&Fပ(?
    filtering G'င&E mapping eဆ1င&B.က&ခ0က&တiuကiuပ8 အလ.ယ&တကJ
    လuပ&eဆ1င&eစGiuင&ပ8သည&
    Before Streams
    public class T1BefStream {

    public static void main(String[] args) {


    List<Integer> list = Arrays.asList(1,2,4,5,6,7,8,9,10);
    int sum = sum(list);
    System.out.println(sum);
    }

    static int sum(List<Integer> list) {


    int sum = 0;
    Iterator<Integer> itr = list.iterator();
    while(itr.hasNext()) {
    sum += itr.next();
    }
    return sum;
    }
    }
    Using Streams
    public class T2UsingStream {

    public static void main(String[] args) {


    List<Integer> list = Arrays.asList(1,2,4,5,6,7,8,9,10);
    int sum = sum(list);
    System.out.println(sum);
    }

    static int sum(List<Integer> list) {


    return list.stream().mapToInt(i -> i).sum();
    }
    }
    What is a Stream?
    • Stream သည& အသu;?2ပuရန&လiuအပ&လ1သK&Eအခ8တ.င& ထuပ&လuပ&eပ?Giuင&eသ1 Data Structure တစ&မ0iu?2ဖစ&
    ပ8သည&

    • Stream မ01?အ1? Data အ1?သiမ&?ဆည&?ရန& အသu;?မ2ပuGiuင&ပD၊ မJလ Data Source မ01?မ' Data မ01?အ1?
    Pipe Line ကDEသiu တစ&ခu2ခင&? စ(?ဆင&?eစက1၊ သတ&မ'တ&ထ1?eသ1 လuပ&eဆ1င&ခ0က&မ01အ1? လuပ&eဆ1င&eစ
    Giuင&ပ8သည&

    • တဖန& Stream ၏ Internal Iteration သည& Stream Operation ၏ Lazy Seeking အ1? ပ;Eပiu?eပ?ပ8သည&

    • Stream မ01?သည& သu;?စ.Dနiuင&eသ1 Object မ01?2ဖစ&Fပ(?၊ Stream အတ.င&?/i Data မ01?အ1? တစ&Nကiမ& သu;?စ.DFပ(?
    ပ8က မJရင&? Stream Object အ1? 2ပန&လည& အသu;?2ပuGiuင&eတ1Eမည& မဟuတ&ပ8

    • Stream တစ&ခuတ.င& creation၊ intermediate process G'င&E terminal process တiuပ8ဝင&<ကFပ(? ပiuက&လiuင&?
    တစ&ခuကDEသiu ခ0iတ&ဆက&လPက&/iပ8သည&

    • Stream အတ.င&?/i Data မ01?အ1? အသu;?2ပuရ1တ.င& Sequential eက1 Parallel လuပ&eဆ1င&မQEကiuပ8


    လuပ&eဆ1င&Giuင&ရန& ပ;Eပiu?ထ1?ပ8သည&
    Types of Streams

    • Stream<T>

    • IntStream

    • LongStream

    • DoubleStream
    Stream Operation
    • Stream Creation Operations မ01?သည& Stream မ01?အ1? စတင& 2ဖစ&eပR
    eစeသ1 Operation မ01?2ဖစ&<ကFပ(? ၎င&? method မ01?၏ return type သည&
    Stream အမ0iu? အစ1?မ01? 2ဖစ&<က၏

    • Intermediate Operations မ01?သည& Pipe Line အတ.င&? လက&ဆင&Eကမ&?


    eဆ1င&B.က&ရeသ1 Operation မ01? 2ဖစ&<ကFပ(?၊ ၎င&? Method မ01?၏ Return
    Type သည& Stream Type တစ&မ0iu?မ0iu? 2ဖစ&Fပ(? eန1က&ဆက&တ.D eဆ1င&B.က&
    ခ0က&မ01?ကiuလည&? လuပ&eဆ1င&eစGiuင&မည& 2ဖစ&သည&

    • Terminal Operations မ01?သည& Stream မ01?အ1? အဆu;?သတ& eစeသ1


    လuပ&eဆ1င& ခ0က&မ01?2ဖစ&<ကသည&။ ၎င&? Method မ01?၏ Return Type
    မ01?သည& Stream မဟuတ&eသ1 အ2ခ1?eသ1 Type တစ&မ0iu?မ0iu? ဒ8မ'မဟuတ&
    void 2ဖစ&ပ8မည&
    Stream Creation

    • Get stream from Arrays or collection

    • From File

    • Giving Range of Numbers and specific elements

    • Generate and Iterate


    From Arrays or Collections
    // from array
    int [] array = {1,2,4,5,6,7,8};
    Arrays.stream(array).forEach(System.out::println);

    // from collection
    Collection<String> col = Arrays.asList("Hello", "Java",
    "I am a developer");
    col.stream().forEach(System.out::println);
    From a file

    public static void main(String[] args) throws IOException {

    Files.lines(Paths.get("T2FromFiles.txt"))
    .forEach(System.out::println);

    }
    Ranging
    // IntStream
    IntStream.range(1, 10).forEach(System.out::println);
    IntStream.rangeClosed(1, 10).forEach(System.out::println);

    // LongStream
    LongStream.range(1, 10)
    .forEach(System.out::println);

    // DoubleStream
    DoubleStream.of(19.001, 12.201,11,111)
    .forEach(System.out::println);
    Iterate & Generate
    // double stream generate
    DoubleStream.generate(Math::random).limit(20)
    .forEach(System.out::println);

    // int stream iterate


    IntStream.iterate(0, a -> a + 1).limit(10)
    .forEach(System.out::println);

    // Stream iterate
    Stream.iterate("", a -> a + "a").limit(10)
    .forEach(System.out::println);
    Intermediate Operations
    Method Description

    filter Stream အတ#င%&'i Data မ*+&အ+& စစ%ထuတ%/iuင%သည%

    map အ2ခ+&eသ+ Data ပu6စ6တစ%မ*iu&သiue2ပ+င%&လ:/iuင%သည%

    flatMap Collection Stream မ*+&အ+& Element Stream အ2ဖစ%e2ပ+င%&eပ&သည%

    distinct တ<ည=eသ+ Data မ*+&အ+& တစ%ခuတည%&2ဖစ%eအ+င%2ပuလuပ%/iuင%သည%

    sorted Data မ*+&အ+& အစ=အစ>%တက*2ဖစ%eအ+င% စ=စ>%eပ&/iuင%သည%

    limit Parameter အထi Data မ*+&အ+& က/%@သတ% eပ&/iuင%သည%

    skip Parameter မeရ+က%ခင% Data မ*+&အ+& Skip လuပ%eပ&မည%2ဖစ%သည%


    Filter

    public static void main(String[] args) {


    T0Common.getUser().stream()
    .filter(a -> a.getAge() > 20)
    .map(a -> a.getName()).forEach(System.out::println);
    }
    Map
    public static void main(String[] args) {
    // mapping User to String
    T0Common.getUser().stream()
    .map(a -> a.getName())
    .forEach(System.out::println);

    // mapping User to int


    int sum = T0Common.getUser().stream()
    .mapToInt(a -> a.getAge()).sum();

    System.out.println(sum);
    }
    FlatMap
    public static void main(String[] args) {
    // flat mapping list stream
    T0Common.listStream()
    .flatMap(l -> l.stream().map(a -> a.getName()))
    .sorted()
    .forEach(System.out::println);
    }
    Others
    IntStream
    .of(1,2,3,4,5,6,4,3,2,5,6,7,8,9,4,4,3,2,1)
    .distinct()
    .sorted()
    .skip(3)
    .limit(5)
    .forEach(System.out::println);
    Terminal Operation
    Method Description

    forEach Stream အတ#င%&'i Data မ*+&အ+& တစ%ခuစ=အသu6:2ပu/iuင%ပBသည%

    forEachOrdered Parallel Stream အတ#င%&'i Data မ*+&အ+&အစ=အစ>%အလiuက% တစ%ခuစ=


    အသu6&2ပu/iuင%ပBသည%

    reduce Stream အတ#င:% 'i Data မ*+&အ+& eန+က%ဆu6&တစ%ခu အထi eလE+@ခ* eဆ+င%F#က%
    eပ&/iuင%ပBသည%

    collect Stream အတ#င%&မG Data မ*+&အ+& Container တစ%ခu2ဖင%@ စuစည%&/iuင%ပBသည%

    allMatch Stream အတ#င%&'i Data မ*+&အ+&လu6&သည% Parameter Predicate /Gင%@ကiuက%


    ည=မH@'iမ'iကiu စစ%eဆ&eပ&/iuင%ပBသည%

    anyMatch Stream အတ#င%&'i Data တစ%ခuခuသည% Parameter Predicate /Gင%@ကiuက%ည=မH@


    'i မ'iကiu စစ%eဆ&eပ&/iuင%ပBသည%
    Terminal Operation
    Method Description

    nonMatch Stream အတ#င%&'i Data မ*+&သည% Parameter Predicate /Gင%@ကiuက%ည=


    မH@ မ'ieIက+င%&ကiu စစ%eဆ&eပ&/iuင%ပBသည%

    findFirst Stream Object မGစ=&ဆင%&လ+eသ+ Data မ*+&၏ ပထမဉ=&ဆu6& Data


    အ+& ရယ<eပ&/iuင%ပBသည%

    findAny Stream အတ#င%&'i Element တစ%ခuခu Optional Object 2ဖင%@ 2ပန%eပ&


    မည% 2ဖစ%သည%

    min / max အLက=&ဆu6& သiuမဟuတ% အငယ%ဆu6& Element ကiu '+eဖ#eပ&/iuင%မည% 2ဖစ%သည%

    count လက%'i Stream အတ#င%&'i Element အeရအတ#က%အ+& '+eဖ#eပ&/iuင%


    ပBသည%

    toArray Stream အတ#င%&'i Element မ*+&အ+& Array ပu6စ62ဖင%@ စuစည%&eပ&မည%


    2ဖစ%ပBသည%
    ForEach Vs ForEachOrdered
    IntStream
    .range(1, 10000)
    .parallel()
    .forEachOrdered(System.out::println);

    အကယ& Parallel Stream အ1: အသu;:2ပuပ8က forEach 2ဖင&E iterate လuပ&လPင&


    အစ(အစU&အတiuင&: eဆ1င&B.က&eပ:Giuင&မ မဟuတ&၊ forEachOrdered ကiuသu;:ပ8မ'
    အစ(အစU& အတiuင&: eဆ1င&B.က&eပ:Giuင&
    Reduce

    Stream<User> stream = T0Common.getUser().stream();


    int sum = stream.map(a -> a.getAge())
    .reduce(0, (a, b) -> a + b);
    System.out.println(sum);
    Collect

    List<String> names = T0Common.getUser()


    .stream()
    .map(a -> a.getName())
    .collect(Collectors.toList());

    System.out.println(names);
    AllMatch

    boolean result = T0Common.getUser()


    .stream()
    .allMatch(a -> a.getAge() > 10);

    System.out.println(result);

    You might also like