How to get the output of a program into a Hashmap?

Question

I've a code that goes like this:

public static void displayDirectoryContents(File dir) {
    try {
        File[] files = dir.listFiles();
        for (File file : files) {
            if (file.isDirectory() && !file.getName().endsWith(".svn")) {
                System.out.println("directory:" + file.getCanonicalPath());
                displayDirectoryContents(file);
            } else {
                System.out.println("file:" + file.getCanonicalPath());
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Now, is there a way to put the result set into a hashmap?

Answer 1

You have lots of nesting of objects, so hashmap could be not so good data structure. I would suggest to introduce the custom POJO and tree-like structure:

class Node { String canonicalPath; String type; Node parent; List<Node> children = new ArrayList<>(); }

And modified your code :

public List<Node> displayDirectoryContents(File dir, Node parent) {

List<Node> result = new ArrayList<Node>();
try {
    File[] files = dir.listFiles();
    for (File file : files) {
        if (file.isDirectory() && !file.getName().endsWith(".svn")) {
            Node directory = new Node(file.getCanonicalPath(), "directory", parent);
            directory.setChildren(displayDirectoryContents(file, directory);
            result.add( directory );
        } else {
            result.add(new Node(file.getCanonicalPath(), "file", parent);
        }
    }
 } catch (IOException e) {
     e.printStackTrace();
 }
 return result;
}

something like that - and modify than your processing.

or if you need file list with its names :

you can introduce Map<String, Object> , and as Object you can put either String (for file), or Map<String, Object> for folder, and make recursion.

or simply make a List of files, and recursively populate it. with pure file paths, like

List<String> displayDirectoryContents(File dir) {
    List<String> res = new ArrayList();
    File[] files = dir.listFiles();
    for (File file : files) {
        if (file.isDirectory() && !file.getName().endsWith(".svn")) {
            res.add("directory:" + file.getCanonicalPath());
            res.addAll(displayDirectoryContents(file));
        } else {
            res.add("file:" + file.getCanonicalPath());
        }
    }
    return res;
}

and than you can:

displayDirectoryContents("/dummypath").forEach(System.out.println);

will give you the same result.

Or to Concurrent map of string-string

Map<String, String> res = displayDirectoryContents("/dummypath").stream().collect(Collectors.toConcurrentMap(o -> o, o -> o));