java-stream

I am aggregating a bunch of enum values (different from the ordinal values) in a foreach loop. int output = 0; for (TestEnum testEnum: setOfEnums) { output |= testEnum.getValue(); } Is there a way to do this in streams API? If I use a lambda like this in a Stream<TestEnum> : setOfEnums.stream().forEach(testEnum -> (output |= testEnum.getValue()); I get a compile time error that says, 'variable used in lambda should be effectively final'. Predicate represents a boolean valued function, you need to use reduce method of stream to aggregate bunch of enum values. if we consider that you have

In addition to my question asked previously, that can be found here, How to combine list elements and find the price of largest combination Instead of using Integer price , I am using String price , List<Long> highest = details .stream() .map(d -> Stream.concat(Stream.of(d.getDetailId()), d.getStackableDetails().stream()).collect(Collectors.toList())) .collect(Collectors.toMap(s -> s.stream().map(Double.class::cast).reduce(0D, (left, right) -> left + Double.parseDouble(map.get(right).getPrice())), s -> s.stream().collect(Collectors.toList()), (left, right) -> right, TreeMap::new)) .lastEntry()

Closed . This question is opinion-based . It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post . Closed 3 years ago . I am wondering how I could design methods that could either be run concurrently or single threaded. For example I have a method like this: /** * Produces the norm of the two vector {@code v1}. * * @param v1 * The first vector. * * @param v2 * The second vector * * @throws MathException * Of type {@code DIMENSION_MISMATCH} if * {@code v1.getDimension()} is != {@code v2

Consider the following code: List<String> myList = Arrays.asList(1, 2, 3); String[] myArray1 = myList.toArray(new String[myList.size()]); String[] myArray2 = myList.stream().toArray(String[]::new); assert Arrays.equals(myArray1, myArray2); It seems to me that using a stream is much simpler. Therefore, I tested the speed of each. List<String> myList = Arrays.asList("1", "2", "3"); double start; start = System.currentTimeMillis(); for (int i = 0; i < 10_000_000; i++) { String[] myArray1 = myList.toArray(new String[myList.size()]); assert myArray1.length == 3; } System.out.println(System

I've a a stream which I want to partition into smaller parts based on matching Id and then apply some proccessing logic on each of the part/element. class BigRequest{ String bId; List<Parts> parts; //getters and setter here } Class Parts{ String pId; String partId; //getters and setter here } I want to segregate and create a list of Parts of size 10 when the partId of different parts are same. How to use the filter or reduce or groupingBy function to compare the two elements and put them to a list? I've tried filter like below, doesn't take p1 variable: big.stream().filter( p -> p.getPartId()

Does Java 8 Stream.iterator() auto-close the stream when it's done? I suppose not... I have something like this: class Provider implements Serializable { Iterator<String> iterator() { Stream<String> stream = new BufferedReader(...).lines(); return stream.iterator(); } } This iterator is used by some other class that doesn't know the iterator is based on a file-reading resource. That is class Consumer { void f() { Iterator<String> iterator = provider.iterator(); // code that calls iterator methods at non-determined times } } I have to stream the file because it's too large to fit into memory.

This question already has an answer here : Java 8, first processing of a list is slower than the subsequent processing (1 answer) Closed 3 years ago . I ran below sample code in my PC running with Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz (2 CPUs), ~2.7GHz String format = "%7s run taken %6d micro seconds %5d findAny"; // First run long start = System.nanoTime(); int rand = IntStream.range(0, 100000).parallel().findAny().getAsInt(); long end = System.nanoTime(); System.out.println(String.format(format, "First", ((end - start) / 1000), rand)); // Subsequent runs for (int i = 0; i < 25; i++) {

I have nested list and am able to set isMatched and department.setMatchedStatus(true) when if condition is true. boolean isMatched = false; for (Employee employee: company.getEmployees()) { for (Department department: employee.getDepartments()) { if(departmentList.contains(department.getDepartmentName())){ isMatched = true; department.setMatchedStatus(true); } } } return isMatched; Would like to achieve the same using java 8 streams, which i tried using below code, but couldn't return boolean. isMatched = company.getEmployees().stream() .flatMap(employee-> employee.getDepartments().stream())