如何创建从根目录到文件完整路径的映射

Question

I am trying to make a method that compares some root path and a File full path and extract all directories with names and full paths to each directory into a Map

For example lets say I want to make a Map that will looks something like this:

Map<String, File> mapFile = new HashMap<>;
mapFile.put("root", new File("/root"));
mapFile.put("dir1", new File("/root/dir1"));
mapFile.put("dir2", new File("/root/dir1/dir2"));
mapFile.put("dir3", new File("/root/dir1/dir2/dir3"));

Here is the solution that I came so far:

private Map<String, File> fileMap(String rootPath, File file) {
    Map<String, File> fileMap = new HashMap<>();
    String path = file.getPath().substring(rootPath.length()).replaceAll("\\\\", "/");// fu windows....
    String[] chunks = path.split("/");
    String p = rootPath.endsWith("/") ? rootPath.substring(0, rootPath.length() - 1) : rootPath;
    for (String chunk : chunks) {
        if (chunk.isEmpty()) continue;
        p += "/" + chunk;
        fileMap.put(chunk, new File(p));
    }
    return fileMap;
}

And that is how should be used:

Map<String, File> fileMap = fileMap("/root", new File("/root/dir1/dir2/dir3"));
fileMap.forEach((name, path) -> System.out.println(name + ", " + path));

The main problem is that I don't like it and it looks like it is made just to pass the tests...And it looks terrible.

Is there any build in solutions or functionality in Java that can make this more clear. Coding something like this feels like I'm trying to find how to make a boil water. So any help would be appreciated. Thanks.

Answer 1

Use Path class for getting directory name:

private static Map<String, File> fileMap(String rootPath, File file) {
    Map<String, File> fileMap = new HashMap<>();
    fileMap.put(Paths.get(rootPath).getFileName().toString(), new File(rootPath));  // add root path
    Path path = file.toPath();

    while (!path.equals(Paths.get(rootPath))) {
        fileMap.put(path.getFileName().toString(), new File(path.toUri())); // add current dir
        path = path.getParent(); // go to parent dir
    }
    return fileMap;
}

You can even pass Path as an argument directly like

fileMap("/root", new File("/root/dir1/dir2/dir3").toPath());

In this case you don't need File in the method at all

Answer 2

You can just use the file.getParentFile() method to get down the file path until you get to the root directory:

private static Map<String, File> fileMap(String rootPath, File file) {
    if (!file.getAbsolutePath().startsWith(rootPath)) {
        throw new IllegalArgumentException(file.getAbsolutePath() + " is not a child of " + rootPath);
    }
    File root = new File(rootPath);
    Map<String, File> fileMap = new HashMap<>();
    while (!root.equals(file)) {
        fileMap.put(file.getName(), file);
        file = file.getParentFile();
    }
    fileMap.put(root.getName(), root);
    return fileMap;
}