Java 8流发出流 [英] Java 8 stream emitting a stream

问题描述

我有以下文件格式：

Text1
+ continuation of Text1
+ more continuation of Text1 
Text2
+ continuation of Text2
+ more continuation of Text2
+ even more continuation of Text2

Continuations标有 \ n + + 。 （换行符，加上字符，空格作为三个字符的字符串。）Continuations可以是任意数量的行，包括0。

Continuations are marked by \n+. (Newline, plus character, space as a three character string.) Continuations can be any number of lines, including 0.

我想要以下输出（每个都是一行用 .forEach 打印：

I want the following output (each is a line printed with .forEach):

Text1 continuation of Text1 more continuation of Text1 
Text2 continuation of Text2 more continuation of Text2 even more continuation of Text2

我想要仅使用Java流进行转换，最好使用Collect。有没有办法优雅地做到这一点？

I would like to use only Java streams to do the conversion, preferably with Collect. Is there a way to do this elegantly?

编辑：

另一个更现实的例子：

Lorem ipsum dolor sit amet, consectetur 
+ adipiscing elit, sed do eiusmod tempor incididunt 
+ ut labore et dolore magna aliqua. Ut enim ad minim veniam, 
+ quis nostrud exercitation ullamco laboris nisi ut aliquip ex 
+ ea commodo consequat. 
Duis aute irure dolor in reprehenderit in voluptate velit 
+ esse cillum dolore eu fugiat nulla pariatur. Excepteur sint 
+ occaecat cupidatat non proident, sunt in culpa qui officia 
+ deserunt mollit anim id est laborum.

预期结果为两行：

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

推荐答案

在Java 9中，你可以使用

In Java 9, you could use

static final Pattern LINE_WITH_CONTINUATION = Pattern.compile("(\\V|\\R\\+)+");

...

try(Scanner s = new Scanner(file)) {
    s.findAll(LINE_WITH_CONTINUATION)
        .map(m -> m.group().replaceAll("\\R\\+", ""))
        .forEach(System.out::println);
}

由于Java 8缺少 Scanner.findAll（Pattern） 方法，您可以添加操作的自定义实现作为解决方法

Since Java 8 lacks the Scanner.findAll(Pattern) method, you may add a custom implementation of the operation as a work-around

public static Stream<MatchResult> findAll(Scanner s, Pattern pattern) {
    return StreamSupport.stream(new Spliterators.AbstractSpliterator<MatchResult>(
            1000, Spliterator.ORDERED|Spliterator.NONNULL) {
        public boolean tryAdvance(Consumer<? super MatchResult> action) {
            if(s.findWithinHorizon(pattern, 0)!=null) {
                action.accept(s.match());
                return true;
            }
            else return false;
        }
    }, false);
}

可以像

try(Scanner s = new Scanner(file)) {
    findAll(s, LINE_WITH_CONTINUATION)
        .map(m -> m.group().replaceAll("\\R\\+", ""))
        .forEach(System.out::println);
}

这将使未来的迁移变得容易。

which will make the future migration easy.

这篇关于Java 8流发出流的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！