java-stream

I have a stream of words and I would like to sort them according to the occurrence of same elements (=words). e.g.: {hello, world, hello} to Map<String, List<String>> hello, {hello, hello} world, {world} What i have so far: Map<Object, List<String>> list = streamofWords.collect(Collectors.groupingBy(???)); Problem 1: The stream seems to lose the information that he is processing Strings, therefore the compiler forces me to change the type to Object, List Problem 2: I don't know what to put inside the parentesis to group it by the same occurrence. I know that I am able to process single

I have a test code like this : List<Integer> list = new ArrayList<>(1000000); for(int i=0;i<1000000;i++){ list.add(i); } List<String> values = new ArrayList<>(1000000); list.stream().forEach( i->values.add(new Date().toString()) ); System.out.println(values.size()); Running this, I got a correct output: 1000000. However, if I change the stream() to parallelStream() , as this: list.parallelStream().forEach( i->values.add(new Date().toString()) ); I got a random output, e.g.: 920821. What's wrong? Tunaki An ArrayList is not synchronized. Trying to concurrently add elements to it is not defined.

I am trying to implement a word count program in java 8 but I am unable to make it work. The method must take a string as parameter and returns a Map<String,Integer> . When I am doing it in old java way, everthing works fine. But when I am trying to do it in java 8, it returns a map where the keys are the empty with the correct occurrences. Here is my code in a java 8 style : public Map<String, Integer> countJava8(String input){ return Pattern.compile("(\\w+)").splitAsStream(input).collect(Collectors.groupingBy(e -> e.toLowerCase(), Collectors.reducing(0, e -> 1, Integer::sum))); } Here is the

I am writing simple program which will eventually plot the run times of various sorting algorithms written in Java. The general interface of a sorting algorithm is via a method: public void sort(Comparable[] xs) I am attempting to use Java 8's stream mechanism to generate random test cases along the following lines: public static IntStream testCase(int min, int max, int n) { Random generator = new Random(); return generator.ints(min, max).limit(n); } My question is, how can I convert an object of type IntStream to an Integer[] ? You should box the IntStream to a Stream<Integer> , then call