Java 8:列出来自多个路径的文件 [英] Java 8: List files from multiple paths

问题描述

如何在Java 8中从多个路径搜索文件.这些不是子目录或兄弟目录.例如，如果我想在路径中搜索json文件，则可以:

How to search files from multiple paths in Java 8. These are not sub/sibling directories. For example, if I want to search json files in a path, I have:

try (Stream<Path> stream = Files.find(Paths.get(path), Integer.MAX_VALUE, (p, attrs) -> attrs.isRegularFile() && p.toString().endsWith(".json"))) {
  stream.map((p) -> p.name).forEach(System.out::println);
}

是否有更好的方法来搜索多个路径?还是我必须针对多个路径运行相同的代码?

Is there a better way to search in multiple paths? Or do I have to run the same code for multiple paths?

推荐答案

是的，您可以这样做.假设您具有作为 String 对象的 List 的路径，则可以这样做，

Yes you can do it. Assuming you have paths as a List of String objects, you can do it like so,

List<String> paths = ...;

paths.stream().map(path -> {
    try (Stream<Path> stream = Files.list(Paths.get(path))) {
        return stream.filter(p -> !p.toFile().isDirectory()).filter(p -> p.toString().endsWith(".json"))
                .map(Path::toString).collect(Collectors.joining("\n"));
    } catch (IOException e) {
        // Log your ERROR here.
        e.printStackTrace();
    }
    return "";
}).forEach(System.out::println);

如果您需要摆脱换行符，也可以这样做.

In case if you need to get rid of the new-line character, then it can be done like this too.

paths.stream().map(path -> {
    try (Stream<Path> stream = Files.walk(Paths.get(path))) {
        return stream.filter(p -> !p.toFile().isDirectory()).filter(p -> p.toString().endsWith(".json"))
                .map(Path::toString).collect(Collectors.toList());
    } catch (IOException e) {
        e.printStackTrace();
    }
    return Collections.emptyList();
}).flatMap(List::stream).forEach(System.out::println);

在这里，您将每个路径的所有 .json 文件名放入 List ，然后将它们展平为 String 对象，然后再打印.请注意，此方法涉及的另一个步骤是 flatMap .

Here you get all the .json file names for each path into a List, and then flatten them into a flat stream of String objects before printing. Notice that the additional step involved in this approach which is flatMap.

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