如何扫描Java中的文件夹？ [英] How to scan a folder in Java?

问题描述

如何在Java中递归地列出文件夹中的所有文件？

How can I get list all the files within a folder recursively in Java?

推荐答案

不知道你想如何表示树？无论如何，这里是一个使用递归扫描整个子树的示例。文件和目录都是一样的。请注意， File.listFiles（）对于非目录，返回null。

Not sure how you want to represent the tree? Anyway here's an example which scans the entire subtree using recursion. Files and directories are treated alike. Note that File.listFiles() returns null for non-directories.

public static void main(String[] args) {
    Collection<File> all = new ArrayList<File>();
    addTree(new File("."), all);
    System.out.println(all);
}

static void addTree(File file, Collection<File> all) {
    File[] children = file.listFiles();
    if (children != null) {
        for (File child : children) {
            all.add(child);
            addTree(child, all);
        }
    }
}

Java 7提供了几个改进。例如， DirectoryStream 每次提供一个结果 - 调用者不必等待所有I / O操作在执行之前完成。这允许增量GUI更新，提前取消等。

Java 7 offers a couple of improvements. For example, DirectoryStream provides one result at a time - the caller no longer has to wait for all I/O operations to complete before acting. This allows incremental GUI updates, early cancellation, etc.

static void addTree(Path directory, Collection<Path> all)
        throws IOException {
    try (DirectoryStream<Path> ds = Files.newDirectoryStream(directory)) {
        for (Path child : ds) {
            all.add(child);
            if (Files.isDirectory(child)) {
                addTree(child, all);
            }
        }
    }
}

注意可怕的null返回值已被IOException替代。

Note that the dreaded null return value has been replaced by IOException.

Java 7还提供了一个 tree walker ：

Java 7 also offers a tree walker:

static void addTree(Path directory, final Collection<Path> all)
        throws IOException {
    Files.walkFileTree(directory, new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
                throws IOException {
            all.add(file);
            return FileVisitResult.CONTINUE;
        }
    });
}

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