Extend an existing flow collector instance

I need a Collector that's nearly identical to Collectors.toSet(), but with a custom finisher. I'd love to be able to do something like: myCollector = Collectors.toSet(); myCollector.setFinisher(myCustomFinisher); and be done, but that doesn't seem po

Sum of subtractions using the Java Stream API

everyone. I've faced a task, that looked pretty simple to me, but I spend like 4 hours and left with nothing. So, let's assume we have simple list of integers like [1, 2, 3, 4, 5] I want to get sum of subtractions for each element - for this list, it

Implementing Collection.stream ()

I have been working on JDK 1.8 for a few days now where I came across some piece of code which was similar to this: List<Integer> list = Arrays.asList(1,2,3,4,5); list.stream(); Now, easy and clean as it may appear to the people who have been workin

A lambda operation similar to a filter that does not break?

I basically would like to do something like: assertEquals(Arrays.asList(1,2,3).stream() .noDiscardingFilter(x -> x!=1) .map(x -> x*10) .collect(Collectors.toList()), Arrays.asList(1,20,30) ) This is an example, I don't need to get an answer on how t

How to wait while parallelStreams is running?

So, let's deal now. I have Parser class where I can get links from html. I've used Jsoup to get links and then I want to add this links to List. I'm using StreamAPI to proceed that. Look at the following code fragment: public static List<Link> getLi

Java - Find a hash table with a maximum size

I have the following data structure: Map<Integer, Map<String,Double>> ---------------- | | a 2 | | 100 | b 1 | | | c 2 | ---------------- | | a 2 | | 101 | c 2 | ---------------- | | a 2 | | 102 | b 1 | | | c 2 | ---------------- GOAL: get the

How to collect a map key-value from a list

Given the following map declaration Map<Integer, Integer> map; I want to collect all the keys and all the values together into a single List<Integer> using a single stream that iterates over the map's entries just once. So far, I have only man

JSON stream output in Spring MVC

My application is built using Spring boot(1.3.3.RELEASE) with spring mvc, spring data jpa hibernate. MySql is the database and Jackson is the Json serializer. On java 8. I want to return a huge data set in my controller method. Instead of retrieving

Does Stream.parallel () use a new thread?

So, I'm trying to get my head around the Stream API introduced in Java 8. I'm trying to make a stream that can run on a separate thread (just for educational purposes) String oracle = "http://www.oracle.com"; URL url = new URL(oracle); BufferedR

Java 8 streaming on the map

I have a map of map on which I want to stream, Map<LocalDate, Map<Integer, List<String>>> mainMap; and remove the values which match another map, Map<LocalDate, List<String>> childMap; Ex. mainMap contains {2016-02-23={120=[1

Check the contents of the archive with the java stream

Consider following ArrayList: [0] => Person [1] => User [2] => Dummy How can one with Java streams check if this arraylist contains any other objects than Person or User ? So that I can make an if statement to return null if it contains only Pers

Double stream

I want to double a Stream (no DoubleStream). Meaning I start with a stream and want to get a new stream where each element of the old stream is streamed twice. So 1,2,3,4,4,5 gives us 1,1,2,2,3,3,4,4,4,4,5,5. Is there such a stream operation?Create a

Why does Stream.allMatch () return true for an empty stream?

My colleague and I had a bug that was due to our assumption that an empty stream calling allMatch() would return false. if (myItems.allMatch(i -> i.isValid()) { //do something } Of course, it is kind of our fault for assuming and not reading document

Sum distances between list points using Java8 Streams

I have a list of points (x,y) and I want to sum the distances between them. In old Java I would do it like this: List<Point> points = ... long sum = 0; for (int i = 0; i < points.size() - 1; i++) { sum += PointUtil.distance(points.get(i), points.

Java 8, Streams to find duplicate items

I am trying to list out duplicate elements in the integer list say for eg, List<Integer> numbers = Arrays.asList(new Integer[]{1,2,1,3,4,4}); using Streams of jdk 8. Has anybody tried out. To remove the duplicates we can use the distinct() api. But

Java 8 equivalent of (RxJava) Observable # onComplete ()

I'm getting to know Java 8 Stream API and I am unsure how to signal to a consumer of a stream that the stream is completed. In my case the results of the stream-pipeline will be written in batches to a database or published on a messaging service. In

Filter the Java stream at 1 and 1 element only

I am trying to use Java 8 Streams to find elements in a LinkedList. I want to guarantee, however, that there is 1 and only 1 match to the filter criteria. Take this code: public static void main(String[] args) { LinkedList<User> users = new LinkedLi

Call the constructor on a double board via Streams

I am wondering if the following is possible with Java 8, for: Patch[][] patches = new Patch[width][depth]; I want to call the constructor using Streams, I know there is Arrays.stream(patches) which would give me a Stream<Patch[]>, so unfortunately I