java stream 8，每六个字打印一行

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() + ") "));
    }  
}

现在我把所有结果都放在一行了。如何在这个Java流中创建逻辑8，将forEach循环中的每5个字放入换行符（System.out.println）。每六个字印一行。

Answer 1

您可以使用流：

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(" "));
}

然后：

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));

输出：

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.

Answer 2

将列表拆分为5个块，并将每个块中的项连接起来。

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("; "))
    ));

注意：流。Java 9中提供了带条件的迭代。纯Java8解决方案可以使用流。使用计算的块数限制：

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("; "))
    ));