From OCP : Oracle Certified Professional Java SE 8 Programmer || Study Guide : Exam 1z0-809 […] Depending on the number of CPUs available in your environment the following is a possible output of the code using a parallel stream […] Even better, the results scale with the number of processors. Scaling is the property … Read more
You can do it with the help of a loop e.g. import java.util.Arrays; public class Main { public static void main(String[] args) { String[] a = { “a”, “b”, “c” }; String[] b = { “d”, “e”, “f” }; String[] result = new String[a.length]; for (int i = 0; i < Math.min(a.length, b.length); i++) { … Read more
Streams might not be the right tool for this task. Why not just add all elments from original list to new list and calculate how many new entries to add after finding the largest id? Something like: List<Fruit> newFruits = new ArrayList<>(); newFruits.addAll(fruits); int N = 10; int toAdd = N – fruits.size(); int maxId … Read more
map.keySet().stream().map(Object::toString).collect(toCollection(LinkedHashSet::new)); solved Keyset to Set of string [closed]
Something like this… List<String> result = Stream.of(“A”, “A”, “BB”, “C”, “BB”, “D”) .collect(Collectors.groupingBy( Function.identity(), Collectors.counting())) .entrySet() .stream() .filter(x -> x.getValue() == 1L) .map(Entry::getKey).collect(Collectors.toList()); System.out.println(result); // [C, D] 2 solved return the list with strings with single occurrence [closed]
If you can work with a Map<String, Long> then you can use this: public Map<String, Long> countCodingsByDate() { return codingHistory.historyDate.stream() .collect(Collectors.groupingBy( Function.identity(), Collectors.counting() )); } Note: This is the normal way to find out the occurances of a Collection. For similar questions, see: 1, 2 2 solved Reworking method with stream usage [duplicate]
Something like this should do it for you : serviceConfigList.stream() .filter(ser -> ser.getValid().equals(“true”)) .forEach(ser -> { Connection.SERVICE_PORT = ser.getPort(); Connection.SERVICE_ADDRESS = ser.getIp(); // other code.. }); PS : I don’t have your complete code. So can’t help more. 4 solved Using Java 8 lambda and Stream for information extraction
As already mentioned in a comment by the user “soon”, this problem can be easily solved with flatMap and map: List<TestSession> list = mapList.entrySet().stream() .flatMap(e1 -> e1.getValue().stream() .map(e2 -> new TestSession(e1.getKey(), e2.getKey(), e2.getValue()))) .collect(Collectors.toList()); solved Convert Map to List with new java 8 streams
The comparator seems correct. The problem seems to be in your filter clause, where you compare the event id to the device id lastDeviceEvent = deviceEvents .stream() .filter (o -> o.getDeviceId().equals(deviceId)) // Original code used getId() .sorted(comparing((DeviceEvent de) -> de.getId()).reversed()) .findFirst() .get(); solved Java 8 comparator not working
First, it would be impossible to create a map of parentId to each childId if there is a list of children in each node because in general case a parentId key may have multiple childId values and this conflict has to be resolved somehow. So, either a Map<Integer, List<Integer>> where List<Integer> contains ids of all … Read more
abstract class ReferencePipeline<P_IN, P_OUT> extends AbstractPipeline<P_IN, P_OUT, Stream<P_OUT>> implements Stream<P_OUT> … It’s ReferencePipeline that implements them. For example: @Override public final boolean anyMatch(Predicate<? super P_OUT> predicate) { return evaluate(MatchOps.makeRef(predicate, MatchOps.MatchKind.ANY)); } 2 solved How does “Stream” in java8 work?
Before mapToDouble you have to use flatMap like this: return collection1.stream() .flatMap(cA -> cA.getCollectionB().stream()) .mapToDouble(ObjectB::getSalary) .sum(); Or you can use map before the flatMap: return collection1.stream() .map(ObjectA::getCollectionB) .flatMap(List::stream) .mapToDouble(ObjectB::getSalary) .sum(); Of you can use flatMapToDouble directly as @Naman mentioned: return collection1.stream() .flatMapToDouble( cA -> cA.getCollectionB().stream().mapToDouble(ObjectB::getSalary) ).sum(); 5 solved Calculate the sum of a field contained … Read more
You are missing the map operator here. You have to add map operator to the stream processing pipeline before collecting it. Here’s how it looks. objList.stream().map(Obj::val).collect(Collectors.joining(“.”)); solved Concat parameters from object list
You can do it as follows: String section = “PRIMARY”; Optional.ofNullable(student) .map( i -> (i.getStandard() > 5) ? “SECONDARY” : section ) .orElse(section); solved How to simplify if statement using Optional.ofNullable() [closed]
peek is just a way to peek inside the stream, it doesn’t change it but the function in peek will receive all the elements that are in the stream. forEach is an terminal operation that will consume all the data in the stream and return void. The result of the above code will be each … Read more