DirectoryStream.Filter用于列出基于特定日期/时间的文件的示例

Question

我试图调查一个DirecoryStream.Filter示例newDirectoryStream,我可以在其中列出超过60天的目录(及其所有子目录)下的所有文件,作为示例.

DirectoryStream<Path> dirS = Files.newDirectoryStream(Paths.get("C:/myRootDirectory"), <DirectoryStream.filter>);

for (Path entry: dirS) {
    System.out.println(entry.toString());
}

在上面的代码中,应该是DirectoryStream.filter什么？
这将是一个很大的帮助,因为我正在一个项目,我试图删除早于某个时间戳和java-1.7 File.listFiles()之前的文件挂起.

可以Files.walkFileTree()提供一个选项吗？

Answer 1

如果我做对了,你有两种情况:

1. 创建自定义filter以选择超过60天的文件
2. 遍历子目录(整个FileTree)并收集您的信息

使用Calendar类实现60天的条件时,自定义过滤器更容易实现:

DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
    @Override
    public boolean accept(Path entry) throws IOException {BasicFileAttributes attr = Files.readAttributes(entry,BasicFileAttributes.class);
    FileTime creationTime = attr.creationTime();
    Calendar cal = Calendar.getInstance();
    int days = cal.fieldDifference(new Date(creationTime.toMillis()),Calendar.DAY_OF_YEAR);
        return (Math.abs(days) > 60);
        }
  };

正常执行只会查找根目录中的文件.要查找子目录,您对使用的猜测walkFileTree()是正确的.

但是,这需要一个FileVisitor接口的实现,一个简单的实现幸运地与7 - 捆绑在一起SimpleFileVisitor.

要遍历子目录,您可以选择覆盖特定于目录的方法 - 我preVisitDirectory在SimpleFileVisitor这里使用过:

Files.walkFileTree(dirs, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path file,
                    BasicFileAttributes attrs) {

由于preVisitDirectory将自定义return FileVisitResult.CONTINUE;以防您没有任何其他限制,我们将利用preVisitDirectory方法在应用过滤器时一次遍历我们的目录1.

Files.walkFileTree(dirs, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path file,
                    BasicFileAttributes attrs) {

                DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
                    @Override
                    public boolean accept(Path entry) throws IOException {
                        BasicFileAttributes attr = Files.readAttributes(entry,
                                BasicFileAttributes.class);
                        FileTime creationTime = attr.creationTime();
                        Calendar cal = Calendar.getInstance();
                        int days = cal.fieldDifference(
                                new Date(creationTime.toMillis()),
                                Calendar.DAY_OF_YEAR);
                        return (Math.abs(days) > 60);
                    }
                };
                try (DirectoryStream<Path> stream = Files.newDirectoryStream(
                        file, filter)) {
                    for (Path path : stream) {
                        System.out.println(path.toString());
                    }
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
                return FileVisitResult.CONTINUE;

            }
        }); 

这将为您提供整个目录和子目录结构中所需过滤条件的文件,完整的主要方法如下:

public static void main(String[] args) throws IOException {
        Path dirs = Paths.get("C:/");

        Files.walkFileTree(dirs, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path file,
                    BasicFileAttributes attrs) {

                DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
                    @Override
                    public boolean accept(Path entry) throws IOException {
                        BasicFileAttributes attr = Files.readAttributes(entry,
                                BasicFileAttributes.class);
                        FileTime creationTime = attr.creationTime();
                        Calendar cal = Calendar.getInstance();
                        int days = cal.fieldDifference(
                                new Date(creationTime.toMillis()),
                                Calendar.DAY_OF_YEAR);
                        return (Math.abs(days) > 60);
                    }
                };
                try (DirectoryStream<Path> stream = Files.newDirectoryStream(
                        file, filter)) {
                    for (Path path : stream) {
                        System.out.println(path.toString());
                    }
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
                return FileVisitResult.CONTINUE;

            }
        });

    }