There are two different aspects. First, there is only a single pipeline which is either sequential or parallel. The choice of sequential or parallel at the inner stream is irrelevant. Note that the downstream consumer you see in the cited code snippet represents the entire subsequent stream pipeline, so in your code, ending with .collect(Collectors.toSet());, … Read more
My approach to bulk operations with chunking is to use a partitioning spliterator wrapper, and another wrapper which overrides the default splitting policy (arithmetic progression of batch sizes in increments of 1024) to simple fixed-batch splitting. Use it like this: Stream<OriginalType> existingStream = …; Stream<List<OriginalType>> partitioned = partition(existingStream, 100, 1); partitioned.forEach(chunk -> … process the … Read more
You could use map() to get a Stream of region lists and then mapToInt to get the number of regions for each country. After that use sum() to get the sum of all the values in the IntStream: countries.stream().map(Country::getRegions) // now it’s a stream of regions .filter(rs -> rs != null) // remove regions lists … Read more
A Stream supports several operations and these operations are divided into intermediate and terminal operations. The distinction between this operations is that an intermediate operation is lazy while a terminal operation is not. When you invoke an intermediate operation on a stream, the operation is not executed immediately. It is executed only when a terminal … Read more
You say you want to sort by value, but you don’t have that in your code. Pass a lambda (or method reference) to sorted to tell it how you want to sort. And you want to get the keys; use map to transform entries to keys. List<Type> types = countByType.entrySet().stream() .sorted(Comparator.comparing(Map.Entry::getValue)) .map(Map.Entry::getKey) .collect(Collectors.toList());
It is possible to get the last element with the method Stream::reduce. The following listing contains a minimal example for the general case: Stream<T> stream = …; // sequential or parallel stream Optional<T> last = stream.reduce((first, second) -> second); This implementations works for all ordered streams (including streams created from Lists). For unordered streams it … Read more
There are new methods added to java.util.Arrays to convert an array into a Java 8 stream which can then be used for summing etc. int sum = Arrays.stream(myIntArray).sum(); Multiplying two arrays is a little more difficult because I can’t think of a way to get the value AND the index at the same time as … Read more
Until you find the element first, you can’t retrieve the attribute values of it. Use findElements method to fetch all links using the following locator table tr td[class=”journalTable-journalPost”] a Then iterate through each element using for-each to fetch id for each element. Sample code: List<WebElement> listOfLinks = driver.findElements(By.cssSelector(“table tr td[class=”journalTable-journalPost”] a”)); for(WebElement link: listOfLinks) { … Read more
In Java 9, you could use static final Pattern LINE_WITH_CONTINUATION = Pattern.compile(“(\\V|\\R\\+)+”); … try(Scanner s = new Scanner(file)) { s.findAll(LINE_WITH_CONTINUATION) .map(m -> m.group().replaceAll(“\\R\\+”, “”)) .forEach(System.out::println); } Since Java 8 lacks the Scanner.findAll(Pattern) method, you may add a custom implementation of the operation as a work-around public static Stream<MatchResult> findAll(Scanner s, Pattern pattern) { return StreamSupport.stream(new Spliterators.AbstractSpliterator<MatchResult>( 1000, … Read more
Well the oracle example is self-explanatory here. First one is this: List<String> l = new ArrayList<>(Arrays.asList(“one”, “two”)); Stream<String> sl = l.stream(); l.add(“three”); String s = l.collect(Collectors.joining(” “)); If you change l by adding one more elements to it before you call the terminal operation (Collectors.joining) you are fine; but notice that the Stream consists of … Read more