CompletableFuture supplyAsync with Stream.map()











up vote
0
down vote

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guys! I have a question: what does this code do:



Collection<Contract.class> contracts = fillTheCollectionFromDb();
contracts.stream().filter(condition)
.map(contractItem ->
CompletableFuture.supplyAsync(() ->
{T result = getAnotherDataFromDb(contractItem);
return result;}, Executor.class)
)//end .map
.map(CompletableFuture::join).collect(Collectors.toList());









share|improve this question






















  • which programming language is it? Looks like Java, but ".class" is used incorrectly in both cases.
    – Alexei Kaigorodov
    Nov 22 at 17:05










  • Java+Spring Boot. Extention .class for example.
    – Alex
    Nov 22 at 20:33

















up vote
0
down vote

favorite












guys! I have a question: what does this code do:



Collection<Contract.class> contracts = fillTheCollectionFromDb();
contracts.stream().filter(condition)
.map(contractItem ->
CompletableFuture.supplyAsync(() ->
{T result = getAnotherDataFromDb(contractItem);
return result;}, Executor.class)
)//end .map
.map(CompletableFuture::join).collect(Collectors.toList());









share|improve this question






















  • which programming language is it? Looks like Java, but ".class" is used incorrectly in both cases.
    – Alexei Kaigorodov
    Nov 22 at 17:05










  • Java+Spring Boot. Extention .class for example.
    – Alex
    Nov 22 at 20:33















up vote
0
down vote

favorite









up vote
0
down vote

favorite











guys! I have a question: what does this code do:



Collection<Contract.class> contracts = fillTheCollectionFromDb();
contracts.stream().filter(condition)
.map(contractItem ->
CompletableFuture.supplyAsync(() ->
{T result = getAnotherDataFromDb(contractItem);
return result;}, Executor.class)
)//end .map
.map(CompletableFuture::join).collect(Collectors.toList());









share|improve this question













guys! I have a question: what does this code do:



Collection<Contract.class> contracts = fillTheCollectionFromDb();
contracts.stream().filter(condition)
.map(contractItem ->
CompletableFuture.supplyAsync(() ->
{T result = getAnotherDataFromDb(contractItem);
return result;}, Executor.class)
)//end .map
.map(CompletableFuture::join).collect(Collectors.toList());






concurrency






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Nov 22 at 16:33









Alex

187




187












  • which programming language is it? Looks like Java, but ".class" is used incorrectly in both cases.
    – Alexei Kaigorodov
    Nov 22 at 17:05










  • Java+Spring Boot. Extention .class for example.
    – Alex
    Nov 22 at 20:33




















  • which programming language is it? Looks like Java, but ".class" is used incorrectly in both cases.
    – Alexei Kaigorodov
    Nov 22 at 17:05










  • Java+Spring Boot. Extention .class for example.
    – Alex
    Nov 22 at 20:33


















which programming language is it? Looks like Java, but ".class" is used incorrectly in both cases.
– Alexei Kaigorodov
Nov 22 at 17:05




which programming language is it? Looks like Java, but ".class" is used incorrectly in both cases.
– Alexei Kaigorodov
Nov 22 at 17:05












Java+Spring Boot. Extention .class for example.
– Alex
Nov 22 at 20:33






Java+Spring Boot. Extention .class for example.
– Alex
Nov 22 at 20:33














1 Answer
1






active

oldest

votes

















up vote
0
down vote



accepted










this code is equivalent to:



Collection<Contract> contracts = fillTheCollectionFromDb();
contracts.stream().filter(condition)
.map(this::getAnotherDataFromDb)
.collect(Collectors.toList());


To make this program truly parallel, it should be modified. First, launch all the requests to database in parallel:



Collection<Contract> contracts = fillTheCollectionFromDb();
List<CompletableFuture> futures = contracts.stream().filter(condition)
.map(contractItem ->
CompletableFuture.supplyAsync(
()->getAnotherDataFromDb(contractItem),
executor)
)//end .map
.collect(Collectors.toList());


and only after that collect all the results:



List results = futures.stream
.map(CompletableFuture::join)
.collect(Collectors.toList());





share|improve this answer





















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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    0
    down vote



    accepted










    this code is equivalent to:



    Collection<Contract> contracts = fillTheCollectionFromDb();
    contracts.stream().filter(condition)
    .map(this::getAnotherDataFromDb)
    .collect(Collectors.toList());


    To make this program truly parallel, it should be modified. First, launch all the requests to database in parallel:



    Collection<Contract> contracts = fillTheCollectionFromDb();
    List<CompletableFuture> futures = contracts.stream().filter(condition)
    .map(contractItem ->
    CompletableFuture.supplyAsync(
    ()->getAnotherDataFromDb(contractItem),
    executor)
    )//end .map
    .collect(Collectors.toList());


    and only after that collect all the results:



    List results = futures.stream
    .map(CompletableFuture::join)
    .collect(Collectors.toList());





    share|improve this answer

























      up vote
      0
      down vote



      accepted










      this code is equivalent to:



      Collection<Contract> contracts = fillTheCollectionFromDb();
      contracts.stream().filter(condition)
      .map(this::getAnotherDataFromDb)
      .collect(Collectors.toList());


      To make this program truly parallel, it should be modified. First, launch all the requests to database in parallel:



      Collection<Contract> contracts = fillTheCollectionFromDb();
      List<CompletableFuture> futures = contracts.stream().filter(condition)
      .map(contractItem ->
      CompletableFuture.supplyAsync(
      ()->getAnotherDataFromDb(contractItem),
      executor)
      )//end .map
      .collect(Collectors.toList());


      and only after that collect all the results:



      List results = futures.stream
      .map(CompletableFuture::join)
      .collect(Collectors.toList());





      share|improve this answer























        up vote
        0
        down vote



        accepted







        up vote
        0
        down vote



        accepted






        this code is equivalent to:



        Collection<Contract> contracts = fillTheCollectionFromDb();
        contracts.stream().filter(condition)
        .map(this::getAnotherDataFromDb)
        .collect(Collectors.toList());


        To make this program truly parallel, it should be modified. First, launch all the requests to database in parallel:



        Collection<Contract> contracts = fillTheCollectionFromDb();
        List<CompletableFuture> futures = contracts.stream().filter(condition)
        .map(contractItem ->
        CompletableFuture.supplyAsync(
        ()->getAnotherDataFromDb(contractItem),
        executor)
        )//end .map
        .collect(Collectors.toList());


        and only after that collect all the results:



        List results = futures.stream
        .map(CompletableFuture::join)
        .collect(Collectors.toList());





        share|improve this answer












        this code is equivalent to:



        Collection<Contract> contracts = fillTheCollectionFromDb();
        contracts.stream().filter(condition)
        .map(this::getAnotherDataFromDb)
        .collect(Collectors.toList());


        To make this program truly parallel, it should be modified. First, launch all the requests to database in parallel:



        Collection<Contract> contracts = fillTheCollectionFromDb();
        List<CompletableFuture> futures = contracts.stream().filter(condition)
        .map(contractItem ->
        CompletableFuture.supplyAsync(
        ()->getAnotherDataFromDb(contractItem),
        executor)
        )//end .map
        .collect(Collectors.toList());


        and only after that collect all the results:



        List results = futures.stream
        .map(CompletableFuture::join)
        .collect(Collectors.toList());






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 23 at 4:45









        Alexei Kaigorodov

        9,70811028




        9,70811028






























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