Arrays.stream(int[]) creates an IntStream, not a Stream<Integer>. So you need to call mapToObj instead of just map, when mapping an int to an object. This should work as expected: String commaSeparatedNumbers = Arrays.stream(numbers) .mapToObj(i -> ((Integer) i).toString()) //i is an int, not an Integer .collect(Collectors.joining(“, “)); which you can also write: String commaSeparatedNumbers = Arrays.stream(numbers) … Read more
You can use Collections.frequency: numbers.stream().filter(i -> Collections.frequency(numbers, i) >1) .collect(Collectors.toSet()).forEach(System.out::println);
The Java 8 streams library is primarily geared toward splitting streams into smaller chunks for parallel processing, so stateful pipeline stages are quite limited, and doing things like getting the index of the current stream element and accessing adjacent stream elements are not supported. A typical way to solve these problems, with some limitations, of … Read more
Your assumption is correct. Your stream implementation is slower than the for-loop. This stream usage should be as fast as the for-loop though: EXCLUDE_PATHS.stream() .map(String::toLowerCase) .anyMatch(path::contains); This iterates through the items, applying String::toLowerCase and the filter to the items one-by-one and terminating at the first item that matches. Both collect() & anyMatch() are terminal operations. … Read more
You may either convert the stream to IntStream: OptionalInt max = list.stream().mapToInt(Integer::intValue).max(); Or specify the natural order comparator: Optional<Integer> max = list.stream().max(Comparator.naturalOrder()); Or use reduce operation: Optional<Integer> max = list.stream().reduce(Integer::max); Or use collector: Optional<Integer> max = list.stream().collect(Collectors.maxBy(Comparator.naturalOrder())); Or use IntSummaryStatistics: int max = list.stream().collect(Collectors.summarizingInt(Integer::intValue)).getMax();
The reason for this is the use of Optional<T> in the return. Optional is not allowed to contain null. Essentially, it offers no way of distinguishing situations “it’s not there” and “it’s there, but it is set to null“. That’s why the documentation explicitly prohibits the situation when null is selected in findFirst(): Throws: NullPointerException … Read more
To Remove element from the list objectA.removeIf(x -> conditions); eg: objectA.removeIf(x -> blockedWorkerIds.contains(x)); List<String> str1 = new ArrayList<String>(); str1.add(“A”); str1.add(“B”); str1.add(“C”); str1.add(“D”); List<String> str2 = new ArrayList<String>(); str2.add(“D”); str2.add(“E”); str1.removeIf(x -> str2.contains(x)); str1.forEach(System.out::println); OUTPUT: A B C
For completeness, here is a Guava solution. Iterators.partition(stream.iterator(), batchSize).forEachRemaining(this::process); In the question the collection is available so a stream isn’t needed and it can be written as, Iterables.partition(data, batchSize).forEach(this::process);
If I understand correctly you want a functional interface with a method void m(). In which case you can simply use a Runnable.
This may be sufficient in many cases stream.findAny().isPresent()