mjhjmtu

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...

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));

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

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

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);