Question

I’ve an ArrayList<String> containing paths of directiories, like:

/home, /usr...

I want to write a code that will remove all the paths from the list if the list already contains parent direcotry of that element.
For e.g:
If the list contains:

/home
/home/games

then, /home/games should get removed as its parent /home is already in the list.
Below is the code:

for (int i = 0; i < checkedList.size(); i++) {
            File f = new File(checkedList.get(i));
            if(checkedList.contains(f.getParent()));
            checkedList.remove(checkedList.get(i));
}

Above checkedList is a String arrayList.

The problem comes when the list contains:

/home
/home/games/minesweeper

Now the minesweeper folder will not get removed as its parent games is not in the list. How to remove these kinds of elements too?

Answer 1

Another possible solution would be using String.startsWith(String).

---

But of course you could take advantage of parent functionality of File class in order to handle the relative directories and other particularities. Follows a draft of the solution:

List<String> listOfDirectories = new ArrayList<String>();
listOfDirectories.add("/home/user/tmp/test");
listOfDirectories.add("/home/user");
listOfDirectories.add("/tmp");
listOfDirectories.add("/etc/test");
listOfDirectories.add("/etc/another");

List<String> result = new ArrayList<String>();

for (int i = 0; i < listOfDirectories.size(); i++) {
    File current = new File(listOfDirectories.get(i));
    File parent = current;
    while ((parent = parent.getParentFile()) != null) {
        if (listOfDirectories.contains(parent.getAbsolutePath())) {
            current = parent;
        }
    }
    String absolutePath = current.getAbsolutePath();
    if (!result.contains(absolutePath)) {
        result.add(absolutePath);
    }
}

System.out.println(result);

This would print:

[/home/user, /tmp, /etc/test, /etc/another]