java stream 8, every sixth word print in new line

Question

public class Histogram {
    public static void main(String[] args) throws IOException {
        Stream<String> stream = Files.lines(Paths.get("words.txt"));
        ArrayList<String> list = (ArrayList<String>) stream
                .map(w -> w.split("\\.|\\s+|,")).flatMap(Arrays::stream)
                .filter(x-> x.length() != 0)
                .collect(Collectors.toList());
        list.forEach(s -> System.out.print(s + "(" + s.length() + ") "));
    }  
}

Now I have all results in one line. How I can make logic in this Java stream 8, to put every 5 words from forEach loop to newline (System.out.println). Every sixth word is printed in a new line.

Use a regular for loop (`list.forEach` or `for-each` in general) hides the iterator; so you can't tell when you're at the sixth word. — Elliott Frisch, Nov 17 '21 at 21:21
Does this answer your question? [Take every nth element from a Java 8 stream](https://stackoverflow.com/questions/31602425/take-every-nth-element-from-a-java-8-stream) — Sam, Nov 17 '21 at 21:28
Don’t cast the result of `collect(Collectors.toList())` to `ArrayList`. The documentation doesn’t specify what list you can expect and there is no reason not to use just `List list = …`. By the way, instead of `x.length() != 0` you can write `! x.isEmpty()` — Holger, Nov 18 '21 at 09:50

Nowhere Man · Accepted Answer · 2021-11-18T10:15:15.010

Split the list into chunks of 5 and join the items inside each chunk.

IntStream.iterate(0, i -> i < list.size(), i -> i + 5)
    .forEach(i -> System.out.println(
        IntStream.range(i, Math.min(i + 5, list.size()))
            .mapToObj(list::get)
            .map(s -> s + "(" + s.length() + ")")
            .collect(Collectors.joining("; "))
    ));

Note: Stream.iterate with condition is available in Java 9. Pure Java 8 solution could use Stream.limit with a calculated number of chunks:

IntStream.iterate(0, i -> i + 5)
    .limit(list.size() / 5 + (list.size() % 5 > 0 ? 1 : 0))
    .forEach(i -> System.out.println(
        IntStream.range(i, Math.min(i + 5, list.size()))
            .mapToObj(list::get)
            .map(s -> s + "(" + s.length() + ")")
            .collect(Collectors.joining("; "))
    ));

Oboe · Answer 2 · 2021-11-17T22:11:23.417

You can use stream:

private static final String NEW_LINE = System.lineSeparator();

public static String addNewLines(String str, int n) {
    
    String[] words = str.split(" ");
    
    int size = words.length;
    
    int lines = (int) Math.round((double) size / n);
    
    int lastLine = size - lines * n;
    
    return IntStream.range(0, lines)
            .mapToObj(i -> toString(words, i * n, i * n + n))
            .collect(Collectors.joining(NEW_LINE, "", lastLine > 0 
                            ? NEW_LINE + toString(words, size - lastLine, size)
                            : ""));
}

private static String toString(String[] words, int start, int end) {
    return Arrays.stream(words, start, end).collect(Collectors.joining(" "));
}

Then:

String str = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam egestas maximus augue, in vehicula erat dictum quis. Sed rhoncus tempor maximus. Etiam tempus tristique ex et imperdiet.";

System.out.println(addNewLines(str, 5));

Output:

Lorem ipsum dolor sit amet,
consectetur adipiscing elit. Nam egestas
maximus augue, in vehicula erat
dictum quis. Sed rhoncus tempor
maximus. Etiam tempus tristique ex
et imperdiet.

java stream 8, every sixth word print in new line

2 Answers2