Java Coding Problems

Counting

Counting the number of words in a piece of text is a common problem that can be solved by count():

String str = "Lorem Ipsum is simply dummy text ...";long numberOfWords = Stream.of(str)  .map(w -> w.split("\\s+"))  .flatMap(Arrays::stream)  .filter(w -> w.trim().length() != 0)  .count();

But let's see how many Melon weighing 3,000 there are in our stream:

long nrOfMelon = melons.stream()  .filter(m -> m.getWeight() == 3000)  .count();

We can use the collector that's returned by the counting() factory method:

long nrOfMelon = melons.stream()  .filter(m -> m.getWeight() == 3000)  .collect(Collectors.counting());

We can also use the clumsy approach of using reducing():

long nrOfMelon = melons.stream()  .filter(m -> m.getWeight() == 3000) .collect(Collectors.reducing(0L, ...