Best way to sort strings of filepaths into a directory structure?

Question

I am using contentService.streamDirectory to get a callback containing all directories/files within a BitBucket project, then I am using a for loop and "callback.getFiles().get(i).toString()" to print out each filepath in a web page using a writer object. It looks something like this:

folder_1/file_1.txt
folder_1/file_2.txt
folder_2/folder_3/file_3.txt
folder_2/file_4.txt

What I want to do is generate something that resembles the directory structure and groups by folders, like this:

folder_1
- file_1.txt
- file_2.txt
folder_2
- folder_3
  - file_3.txt
- file_4.txt

I'm a bit unsure how to go about this. The current method for printing out is as follows:

resp.setContentType("text/html");
resp.getWriter().print("<html><body><p>Repository: " + repo.getName() +);
for (int i = 0; i < callback.getFiles().size(); i++) {
    resp.getWriter().println("<p><a href=\"/\">" + callback.getFiles().get(i).toString() + "</a></p>");
}
resp.getWriter().print("</body></html>");

I'm sure a whole lot of loops are required, I know there's a Files.walk() method but it looks like you point to the starting folder within the computer files, I do not know if its possible to point this to BitBucket? Thanks for any help you can give.

What is the type of callback.getFiles()? A list of java.io.File, java.nio.file.Path, or something different? — Holger
– Holger, Commented Jun 24, 2022 at 9:00
@Holger I believe its this: java.lang.Object -> com.atlassian.bitbucket.content.File — MillieJA
– MillieJA, Commented Jun 24, 2022 at 9:07

Holger · Accepted Answer · 2022-06-24 09:40:18Z

A simple approach is to store the elements into a small data structure reflecting the hierarchy first.

Let’s start with a simple stand-alone example to illustrate the approach.

public static void main(String[] args) throws IOException {
    List<Path> files = Arrays.asList(
        Paths.get("folder_1", "file_1.txt"),
        Paths.get("folder_1", "file_2.txt"),
        Paths.get("folder_2", "folder_3", "file_3.txt"),
        Paths.get("folder_2", "file_4.txt")
    );
    System.out.print("<html><body><p>Repository: " + "Test");
    Node root = new Node(null);
    for(Path f: files) root.add(f);
    root.writeTo(System.out);
    System.out.println("</body></html>");
}
static final class Node {
    final String name;
    final Map<String, Node> children = new LinkedHashMap<>();

    Node(String name) { this.name = name; }
    void add(Path path) {
        Node n = this;
        for(Path component: path)
            n = n.children.computeIfAbsent(component.toString(), Node::new);
    }
    void writeTo(Appendable w) throws IOException {
        if(name != null) w.append("<li>").append(name).append('\n');
        if(!children.isEmpty()) {
            w.append("<ul>\n");
            for(Node ch: children.values()) ch.writeTo(w);
            w.append("</ul>\n");
        }
    }
}

This produces

<html><body><p>Repository: Test<ul>
<li>folder_1
<ul>
<li>file_1.txt
<li>file_2.txt
</ul>
<li>folder_2
<ul>
<li>folder_3
<ul>
<li>file_3.txt
</ul>
<li>file_4.txt
</ul>
</ul>
</body></html>

To adapt it to your case, we have to change the add method. Assuming that you’re using this File class, it would be something like

void add(File file) {
    Node n = this;
    for(String component: file.getPath().getComponents())
        n = n.children.computeIfAbsent(component, Node::new);
}

and the adapted caller

resp.setContentType("text/html");
resp.getWriter().print("<html><body><p>Repository: " + repo.getName());
Node root = new Node(null);
for(int i = 0; i < callback.getFiles().size(); i++) root.add(callback.getFiles().get(i));
root.writeTo(resp.getWriter());
resp.getWriter().print("</body></html>");

Hi @Holger , Thanks so much for this, I almost have it! I have tried what you suggested and realised I missed a bit about the callback which makes this not work. I have added a new question now I understand the issue a bit better and its a bit more direct to what I want. It is here if you would like to take a look and see if you can offer any help stackoverflow.com/questions/73123907/… . Thanks!

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