文件的絕對路徑

Question

我在我的系統中搜索一個文件，但這個文件在其他系統下可能有不同的路徑，這意味着當我搜索file.txt它一直在 /f1/f2/file.txt 下，但對於另一個系統，它可以就像一個系統中的c:/programme/f1/f2/file.txt但d:/system/f1/f2/file.txt我試過這個，但它不讀取絕對路徑

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 ，或者是錯誤的

Answer 1

tl; 博士

在f1\\\\f2\\\\之前刪除反斜杠 / -es ，它會阻止 / 他們阻止正確解析父路徑。

例子：

以下代碼使用中間路徑和文件名解析給定的根路徑（根據您的示例盡可能長）：

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());
}

輸出是這樣的：

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

編輯

如果您想在文件樹中搜索已知子路徑，您可以實現一個java.nio.file.FileVisitor如下所示：

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;
    }

}

並以某種方式使用它類似於這個最小的例子：

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();
    }
}

結果將是沒有結果的完整遍歷（如果驅動器上不存在子路徑）或像這樣的簡單打印輸出：

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