文件的绝对路径

Question

我在我的系统中搜索一个文件，但这个文件在其他系统下可能有不同的路径，这意味着当我搜索 file.txt 时，它一直在 /f1/f2/file.txt 下，但系统另一种可能是c:/programme/f1/f2/file.txt 在一个系统中，但d:/system/f1/f2/file.txt 我试过了，但它没有读取绝对路径

String filename = "file.txt";
Path path = Paths.get("\\f1\\f2\\");
Path absPath= path.toAbsolutePath(); 
File file = new File(absPath, filename);

然后我只是得到c:\f1\f2\file.txt，或者它是错误的

Answer 1

tl;博士

去掉f1\\f2\\之前的反斜杠/-es，它会阻止/它们阻止父路径的正确解析。

示例：

以下代码使用中间路径和文件名解析给定的根路径（根据您的示例尽可能长）：

public static void main(String[] args) {
    String fileName = "file.txt";

    // your problem was leading backslash here
    Path subPath = Paths.get("f1\\f2");

    // create the root paths
    Path rootOnC = Paths.get("c:\\programme");
    Path rootOnD = Paths.get("d:\\system");

    // resolve the subpaths and the filename on the root paths
    Path fullPathOnC = rootOnC.resolve(subPath).resolve(fileName);
    Path fullPathOnD = rootOnD.resolve(subPath).resolve(fileName);

    // print the toString representation of their absolute path
    System.out.println("[C:]\t" + fullPathOnC.toAbsolutePath().toString());
    System.out.println("[D:]\t" + fullPathOnD.toAbsolutePath().toString());
}

输出是这样的：

[C:]    c:\programme\f1\f2\file.txt
[D:]    d:\system\f1\f2\file.txt

编辑

如果你想在文件树中搜索一个已知的子路径，你可以像这样实现java.nio.file.FileVisitor：

class PathFinder implements FileVisitor<Path> {

    private Path subPathToBeFound;

    public PathFinder(Path subPathToBeFound) {
        this.subPathToBeFound = subPathToBeFound;
    }

    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        if (file.endsWith(subPathToBeFound)) {
            // print the full path that contained the given subpath
            System.out.println("Subpath found in " + file.toAbsolutePath().toString());
            return FileVisitResult.TERMINATE;
        } else {
            return FileVisitResult.CONTINUE;    
        }
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
        System.err.println("Visit failed: " + exc.getMessage());
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
        return FileVisitResult.CONTINUE;
    }

}

并以某种方式使用它类似于这个最小的例子：

public static void main(String[] args) {
    String fileName = "file.txt";

    // resolve the file name on the subpath
    Path subPath = Paths.get("f1\\f2").resolve(fileName);

    // create a file visitor
    PathFinder pf = new PathFinder(subPath);

    /*
     * this example finds all available drives programmatically
     * and walks the file tree of each one
     */
    try {
        for (Path root : FileSystems.getDefault().getRootDirectories()) {
            System.out.println("Searching in " + root.toAbsolutePath().toString());
            Files.walkFileTree(root, pf);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

结果可能是没有结果的完整遍历（如果驱动器上不存在子路径）或像这样的简单打印输出：

Subpath found in C:\programme\f1\f2\file.txt