How do I list, map and “print if count>0” with Java 8 / stream API?












12















Here's my code as per now.



List<Cat> cats = petStore.getCatsForSale();



if (!cats.empty) 

    logger.info("Processing for cats: " + cats.size());



for (Cat cat : cats) {

    cat.giveFood();

}


My colleague writes realy nice code using the Java stream API. I tried to rewrite it as one streaming statement, but I got stuck.



petStore.getCatsForSale().stream.forEach(cat -> cat.giveFood)

    .countTheCats().thenDo(logger.info("Total number of cats: " + x)); // Incorrect... is this possible?


How can I do this? Ideally I want a single streaming statement...






java java-8 functional-programming java-stream







share|improve this question




















  • 2





    What is count? Do you expect a log statement for every non empty cat?

    – Tim Biegeleisen
    16 hours ago
















12















Here's my code as per now.



List<Cat> cats = petStore.getCatsForSale();



if (!cats.empty) 

    logger.info("Processing for cats: " + cats.size());



for (Cat cat : cats) {

    cat.giveFood();

}


My colleague writes realy nice code using the Java stream API. I tried to rewrite it as one streaming statement, but I got stuck.



petStore.getCatsForSale().stream.forEach(cat -> cat.giveFood)

    .countTheCats().thenDo(logger.info("Total number of cats: " + x)); // Incorrect... is this possible?


How can I do this? Ideally I want a single streaming statement...






java java-8 functional-programming java-stream







share|improve this question




















  • 2





    What is count? Do you expect a log statement for every non empty cat?

    – Tim Biegeleisen
    16 hours ago














12












12








12


1






Here's my code as per now.



List<Cat> cats = petStore.getCatsForSale();



if (!cats.empty) 

    logger.info("Processing for cats: " + cats.size());



for (Cat cat : cats) {

    cat.giveFood();

}


My colleague writes realy nice code using the Java stream API. I tried to rewrite it as one streaming statement, but I got stuck.



petStore.getCatsForSale().stream.forEach(cat -> cat.giveFood)

    .countTheCats().thenDo(logger.info("Total number of cats: " + x)); // Incorrect... is this possible?


How can I do this? Ideally I want a single streaming statement...






java java-8 functional-programming java-stream







share|improve this question
















Here's my code as per now.



List<Cat> cats = petStore.getCatsForSale();



if (!cats.empty) 

    logger.info("Processing for cats: " + cats.size());



for (Cat cat : cats) {

    cat.giveFood();

}


My colleague writes realy nice code using the Java stream API. I tried to rewrite it as one streaming statement, but I got stuck.



petStore.getCatsForSale().stream.forEach(cat -> cat.giveFood)

    .countTheCats().thenDo(logger.info("Total number of cats: " + x)); // Incorrect... is this possible?


How can I do this? Ideally I want a single streaming statement...






java java-8 functional-programming java-stream




java java-8 functional-programming java-stream






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 6 hours ago









Peter Mortensen

13.6k1984111




13.6k1984111










asked 16 hours ago









vikingstevevikingsteve

25.6k1179116




25.6k1179116








  • 2





    What is count? Do you expect a log statement for every non empty cat?

    – Tim Biegeleisen
    16 hours ago














  • 2





    What is count? Do you expect a log statement for every non empty cat?

    – Tim Biegeleisen
    16 hours ago








2




2





What is count? Do you expect a log statement for every non empty cat?

– Tim Biegeleisen
16 hours ago





What is count? Do you expect a log statement for every non empty cat?

– Tim Biegeleisen
16 hours ago












4 Answers
4






active

oldest

votes


















8














I am not sure why you want to use streams as the current loop solutions works, but you may as well use a Stream<List<Cat>>:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .flatMap(cats -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    })

    .forEach(Cat::giveFood);


Maybe an optimization:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .peek(cats -> logger.info("Processing for cats: " + cats.size()))

    .flatMap(Collection::stream)

    .forEach(Cat::giveFood);


Or use this other variant:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .mapToInt(cats -> {

        cats.forEach(Cat::giveFood);

        return cats.size();

    })

    .findAny()

    .ifPresent(count -> logger.info("Processing for cats: " + count));





share|improve this answer





















  • 3





    @CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

    – nullpointer
    15 hours ago






  • 3





    @nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

    – Lino
    15 hours ago






  • 1





    @Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

    – Lino
    15 hours ago






  • 3





    @Lino well, it already is! :P

    – nullpointer
    15 hours ago






  • 3





    @vikingsteve Do not prefer fancy streams over readability.

    – ETO
    15 hours ago



















17














Your current code is much better without a stream and can further be cut short to:



if (!cats.isEmpty()) {

    logger.info("Processing for cats: " + cats.size());

}

cats.forEach(Cat::giveFood); // Assuming giveFood is a stateless operation





share|improve this answer


























  • I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

    – Tim Biegeleisen
    15 hours ago













  • I think single streaming statement is what he is looking for.

    – Prashant Zombade
    15 hours ago











  • @TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

    – nullpointer
    15 hours ago











  • Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

    – vikingsteve
    15 hours ago






  • 2





    In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

    – Lino
    15 hours ago



















3














cats.stream()

    .peek(Cat::giveFood)

    .findAny().ifPresent(cat -> logger.info("Processing for cats: " + cats.size()));





share|improve this answer





















  • 4





    Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

    – ETO
    15 hours ago






  • 1





    @ETO Please look at tags. It says java-8!

    – oleg.cherednik
    15 hours ago








  • 3





    @oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

    – Lino
    15 hours ago






  • 2





    @oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

    – ETO
    15 hours ago






  • 3





    Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

    – ETO
    15 hours ago





















1














I agree with @Lino. This is another alternative based on his idea:



List<Cat> cats = petStore.getCatsForSale();



cats.stream().limit(1)

    .flatMap(c -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    }).forEach(Cat::giveFood);





share|improve this answer


























  • Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

    – Lino
    15 hours ago






  • 1





    @Lino because of empty list

    – David Pérez Cabrera
    15 hours ago











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4 Answers
4






active

oldest

votes








4 Answers
4






active

oldest

votes









active

oldest

votes






active

oldest

votes









8














I am not sure why you want to use streams as the current loop solutions works, but you may as well use a Stream<List<Cat>>:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .flatMap(cats -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    })

    .forEach(Cat::giveFood);


Maybe an optimization:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .peek(cats -> logger.info("Processing for cats: " + cats.size()))

    .flatMap(Collection::stream)

    .forEach(Cat::giveFood);


Or use this other variant:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .mapToInt(cats -> {

        cats.forEach(Cat::giveFood);

        return cats.size();

    })

    .findAny()

    .ifPresent(count -> logger.info("Processing for cats: " + count));





share|improve this answer





















  • 3





    @CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

    – nullpointer
    15 hours ago






  • 3





    @nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

    – Lino
    15 hours ago






  • 1





    @Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

    – Lino
    15 hours ago






  • 3





    @Lino well, it already is! :P

    – nullpointer
    15 hours ago






  • 3





    @vikingsteve Do not prefer fancy streams over readability.

    – ETO
    15 hours ago
















8














I am not sure why you want to use streams as the current loop solutions works, but you may as well use a Stream<List<Cat>>:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .flatMap(cats -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    })

    .forEach(Cat::giveFood);


Maybe an optimization:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .peek(cats -> logger.info("Processing for cats: " + cats.size()))

    .flatMap(Collection::stream)

    .forEach(Cat::giveFood);


Or use this other variant:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .mapToInt(cats -> {

        cats.forEach(Cat::giveFood);

        return cats.size();

    })

    .findAny()

    .ifPresent(count -> logger.info("Processing for cats: " + count));





share|improve this answer





















  • 3





    @CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

    – nullpointer
    15 hours ago






  • 3





    @nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

    – Lino
    15 hours ago






  • 1





    @Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

    – Lino
    15 hours ago






  • 3





    @Lino well, it already is! :P

    – nullpointer
    15 hours ago






  • 3





    @vikingsteve Do not prefer fancy streams over readability.

    – ETO
    15 hours ago














8












8








8







I am not sure why you want to use streams as the current loop solutions works, but you may as well use a Stream<List<Cat>>:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .flatMap(cats -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    })

    .forEach(Cat::giveFood);


Maybe an optimization:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .peek(cats -> logger.info("Processing for cats: " + cats.size()))

    .flatMap(Collection::stream)

    .forEach(Cat::giveFood);


Or use this other variant:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .mapToInt(cats -> {

        cats.forEach(Cat::giveFood);

        return cats.size();

    })

    .findAny()

    .ifPresent(count -> logger.info("Processing for cats: " + count));





share|improve this answer















I am not sure why you want to use streams as the current loop solutions works, but you may as well use a Stream<List<Cat>>:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .flatMap(cats -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    })

    .forEach(Cat::giveFood);


Maybe an optimization:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .peek(cats -> logger.info("Processing for cats: " + cats.size()))

    .flatMap(Collection::stream)

    .forEach(Cat::giveFood);


Or use this other variant:



Stream.of(petStore.getCatsForSale())

    .filter(cats -> !cats.isEmpty())

    .mapToInt(cats -> {

        cats.forEach(Cat::giveFood);

        return cats.size();

    })

    .findAny()

    .ifPresent(count -> logger.info("Processing for cats: " + count));






share|improve this answer














share|improve this answer



share|improve this answer








edited 6 hours ago









Peter Mortensen

13.6k1984111




13.6k1984111










answered 15 hours ago









LinoLino

8,43322037




8,43322037








  • 3





    @CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

    – nullpointer
    15 hours ago






  • 3





    @nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

    – Lino
    15 hours ago






  • 1





    @Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

    – Lino
    15 hours ago






  • 3





    @Lino well, it already is! :P

    – nullpointer
    15 hours ago






  • 3





    @vikingsteve Do not prefer fancy streams over readability.

    – ETO
    15 hours ago














  • 3





    @CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

    – nullpointer
    15 hours ago






  • 3





    @nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

    – Lino
    15 hours ago






  • 1





    @Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

    – Lino
    15 hours ago






  • 3





    @Lino well, it already is! :P

    – nullpointer
    15 hours ago






  • 3





    @vikingsteve Do not prefer fancy streams over readability.

    – ETO
    15 hours ago








3




3





@CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

– nullpointer
15 hours ago





@CommonMan not really, its empty vs non-empty here. I doubt Optional would be useful here much.

– nullpointer
15 hours ago




3




3





@nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

– Lino
15 hours ago





@nullpointer I don't really like any of the solutions here except the one from you, I think using Streams for everyday logic is just overkill and makes it extremly hard to understand the simplest of logic

– Lino
15 hours ago




1




1





@Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

– Lino
15 hours ago





@Spara so that I have a "wrapper"-stream around the Cat-list (Stream<List<Cat>>) which allows me to operate on the whole list at once, but still inside the stream. Using cats.stream() though will give you a stream over all cats (Stream<Cat>)

– Lino
15 hours ago




3




3





@Lino well, it already is! :P

– nullpointer
15 hours ago





@Lino well, it already is! :P

– nullpointer
15 hours ago




3




3





@vikingsteve Do not prefer fancy streams over readability.

– ETO
15 hours ago





@vikingsteve Do not prefer fancy streams over readability.

– ETO
15 hours ago













17














Your current code is much better without a stream and can further be cut short to:



if (!cats.isEmpty()) {

    logger.info("Processing for cats: " + cats.size());

}

cats.forEach(Cat::giveFood); // Assuming giveFood is a stateless operation





share|improve this answer


























  • I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

    – Tim Biegeleisen
    15 hours ago













  • I think single streaming statement is what he is looking for.

    – Prashant Zombade
    15 hours ago











  • @TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

    – nullpointer
    15 hours ago











  • Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

    – vikingsteve
    15 hours ago






  • 2





    In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

    – Lino
    15 hours ago
















17














Your current code is much better without a stream and can further be cut short to:



if (!cats.isEmpty()) {

    logger.info("Processing for cats: " + cats.size());

}

cats.forEach(Cat::giveFood); // Assuming giveFood is a stateless operation





share|improve this answer


























  • I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

    – Tim Biegeleisen
    15 hours ago













  • I think single streaming statement is what he is looking for.

    – Prashant Zombade
    15 hours ago











  • @TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

    – nullpointer
    15 hours ago











  • Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

    – vikingsteve
    15 hours ago






  • 2





    In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

    – Lino
    15 hours ago














17












17








17







Your current code is much better without a stream and can further be cut short to:



if (!cats.isEmpty()) {

    logger.info("Processing for cats: " + cats.size());

}

cats.forEach(Cat::giveFood); // Assuming giveFood is a stateless operation





share|improve this answer















Your current code is much better without a stream and can further be cut short to:



if (!cats.isEmpty()) {

    logger.info("Processing for cats: " + cats.size());

}

cats.forEach(Cat::giveFood); // Assuming giveFood is a stateless operation






share|improve this answer














share|improve this answer



share|improve this answer








edited 6 hours ago









Peter Mortensen

13.6k1984111




13.6k1984111










answered 15 hours ago









nullpointernullpointer

47.6k11100192




47.6k11100192













  • I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

    – Tim Biegeleisen
    15 hours ago













  • I think single streaming statement is what he is looking for.

    – Prashant Zombade
    15 hours ago











  • @TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

    – nullpointer
    15 hours ago











  • Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

    – vikingsteve
    15 hours ago






  • 2





    In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

    – Lino
    15 hours ago



















  • I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

    – Tim Biegeleisen
    15 hours ago













  • I think single streaming statement is what he is looking for.

    – Prashant Zombade
    15 hours ago











  • @TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

    – nullpointer
    15 hours ago











  • Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

    – vikingsteve
    15 hours ago






  • 2





    In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

    – Lino
    15 hours ago

















I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

– Tim Biegeleisen
15 hours ago







I'm under the impression that the OP wants to only log the number of non empty cats, not the original collection size.

– Tim Biegeleisen
15 hours ago















I think single streaming statement is what he is looking for.

– Prashant Zombade
15 hours ago





I think single streaming statement is what he is looking for.

– Prashant Zombade
15 hours ago













@TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

– nullpointer
15 hours ago





@TimBiegeleisen well I chose to implement what the actual code really does and considering want a single streaming statement.. is not to check for the functional correctness in the code.

– nullpointer
15 hours ago













Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

– vikingsteve
15 hours ago





Hi and thx for answer. Can this be done in a one liner? Of course I can write "if (!cats.isEmpty()) logger.info("...") but the purpose of this question is to write it with streams

– vikingsteve
15 hours ago




2




2





In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

– Lino
15 hours ago





In my opinion, is this the only acceptable solution. Don't do everything with Streams just because a tutorial told you so, just by looking at every answer here it's clear what the intentions of this one here is, but for every other? It's just a mess

– Lino
15 hours ago











3














cats.stream()

    .peek(Cat::giveFood)

    .findAny().ifPresent(cat -> logger.info("Processing for cats: " + cats.size()));





share|improve this answer





















  • 4





    Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

    – ETO
    15 hours ago






  • 1





    @ETO Please look at tags. It says java-8!

    – oleg.cherednik
    15 hours ago








  • 3





    @oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

    – Lino
    15 hours ago






  • 2





    @oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

    – ETO
    15 hours ago






  • 3





    Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

    – ETO
    15 hours ago


















3














cats.stream()

    .peek(Cat::giveFood)

    .findAny().ifPresent(cat -> logger.info("Processing for cats: " + cats.size()));





share|improve this answer





















  • 4





    Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

    – ETO
    15 hours ago






  • 1





    @ETO Please look at tags. It says java-8!

    – oleg.cherednik
    15 hours ago








  • 3





    @oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

    – Lino
    15 hours ago






  • 2





    @oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

    – ETO
    15 hours ago






  • 3





    Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

    – ETO
    15 hours ago
















3












3








3







cats.stream()

    .peek(Cat::giveFood)

    .findAny().ifPresent(cat -> logger.info("Processing for cats: " + cats.size()));





share|improve this answer















cats.stream()

    .peek(Cat::giveFood)

    .findAny().ifPresent(cat -> logger.info("Processing for cats: " + cats.size()));






share|improve this answer














share|improve this answer



share|improve this answer








edited 15 hours ago

























answered 15 hours ago









oleg.cherednikoleg.cherednik

6,67821118




6,67821118








  • 4





    Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

    – ETO
    15 hours ago






  • 1





    @ETO Please look at tags. It says java-8!

    – oleg.cherednik
    15 hours ago








  • 3





    @oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

    – Lino
    15 hours ago






  • 2





    @oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

    – ETO
    15 hours ago






  • 3





    Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

    – ETO
    15 hours ago
















  • 4





    Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

    – ETO
    15 hours ago






  • 1





    @ETO Please look at tags. It says java-8!

    – oleg.cherednik
    15 hours ago








  • 3





    @oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

    – Lino
    15 hours ago






  • 2





    @oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

    – ETO
    15 hours ago






  • 3





    Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

    – ETO
    15 hours ago










4




4





Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

– ETO
15 hours ago





Starting from java-9 you may leave your cats hungry ))). Execution of peek is not guaranteed anymore. Please read javadoc for more details.

– ETO
15 hours ago




1




1





@ETO Please look at tags. It says java-8!

– oleg.cherednik
15 hours ago







@ETO Please look at tags. It says java-8!

– oleg.cherednik
15 hours ago






3




3





@oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

– Lino
15 hours ago





@oleg.cherednik I think ETO wanted to say that this solution may only work for java-8 which makes it not a favorable solution when one wants to migrate the version upwards :)

– Lino
15 hours ago




2




2





@oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

– ETO
15 hours ago





@oleg.cherednik Yes, I know. Using peek for non-debugging purposes is considered harmful anyway.

– ETO
15 hours ago




3




3





Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

– ETO
15 hours ago







Moreover, starting from February 2019 there is no long-term support of java-8 for cemmercial users. So if you write java-8 code, consider avoiding potential migration bugs. One may not notice that java-9's peek is not working as it did before. Thus your code will have a hidden unobvious bug.

– ETO
15 hours ago













1














I agree with @Lino. This is another alternative based on his idea:



List<Cat> cats = petStore.getCatsForSale();



cats.stream().limit(1)

    .flatMap(c -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    }).forEach(Cat::giveFood);





share|improve this answer


























  • Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

    – Lino
    15 hours ago






  • 1





    @Lino because of empty list

    – David Pérez Cabrera
    15 hours ago
















1














I agree with @Lino. This is another alternative based on his idea:



List<Cat> cats = petStore.getCatsForSale();



cats.stream().limit(1)

    .flatMap(c -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    }).forEach(Cat::giveFood);





share|improve this answer


























  • Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

    – Lino
    15 hours ago






  • 1





    @Lino because of empty list

    – David Pérez Cabrera
    15 hours ago














1












1








1







I agree with @Lino. This is another alternative based on his idea:



List<Cat> cats = petStore.getCatsForSale();



cats.stream().limit(1)

    .flatMap(c -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    }).forEach(Cat::giveFood);





share|improve this answer















I agree with @Lino. This is another alternative based on his idea:



List<Cat> cats = petStore.getCatsForSale();



cats.stream().limit(1)

    .flatMap(c -> {

        logger.info("Processing for cats: " + cats.size());

        return cats.stream();

    }).forEach(Cat::giveFood);






share|improve this answer














share|improve this answer



share|improve this answer








edited 6 hours ago









Peter Mortensen

13.6k1984111




13.6k1984111










answered 15 hours ago









David Pérez CabreraDavid Pérez Cabrera

3,88321231




3,88321231













  • Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

    – Lino
    15 hours ago






  • 1





    @Lino because of empty list

    – David Pérez Cabrera
    15 hours ago



















  • Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

    – Lino
    15 hours ago






  • 1





    @Lino because of empty list

    – David Pérez Cabrera
    15 hours ago

















Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

– Lino
15 hours ago





Why not use an IntStream.range(1)? No need to use cats.stream().limit(1) that way

– Lino
15 hours ago




1




1





@Lino because of empty list

– David Pérez Cabrera
15 hours ago





@Lino because of empty list

– David Pérez Cabrera
15 hours ago


















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