MuntashirAkon/AppManager · error · IllegalArgumentException

Display name is empty

Error message

Display name is empty

What it means

PathImpl.createDirectories() splits the sanitized display name on the file separator; when splitting yields an empty segment array (e.g. the name was only separators like "/"), it throws IllegalArgumentException("Display name is empty"). The library requires at least one concrete directory segment to create. It is a programmer error, not an environment failure.

Source

Thrown at app/src/main/java/io/github/muntashirakon/io/PathImpl.java:436

        }
        for (String name : dirNames) {
            if (name.equals("..")) {
                throw new IOException("Could not create directories in the parent directory.");
            }
        }
        DocumentFile file = createArbitraryDirectories(documentFile, dirNames, dirNames.length);
        return new PathImpl(context, file);
    }

    @NonNull
    public Path createDirectories(@NonNull String displayName) throws IOException {
        displayName = Paths.sanitize(displayName, true);
        if (displayName == null) {
            throw new IOException("Empty display name.");
        }
        String[] dirNames = displayName.split(File.separator);
        if (dirNames.length == 0) {
            throw new IllegalArgumentException("Display name is empty");
        }
        for (String name : dirNames) {
            if (name.equals("..")) {
                throw new IOException("Could not create directories in the parent directory.");
            }
        }
        DocumentFile file = createArbitraryDirectories(documentFile, dirNames, dirNames.length - 1);
        // Special case for the last segment
        String lastSegment = dirNames[dirNames.length - 1];
        Path fsRoot = VirtualFileSystem.getFsRoot(Paths.appendPathSegment(file.getUri(), lastSegment));
        DocumentFile t = fsRoot != null ? fsRoot.documentFile : file.findFile(lastSegment);
        if (t != null) {
            throw new IOException(t.getUri() + " already exists.");
        }
        t = file.createDirectory(lastSegment);
        if (t == null) {
            throw new IOException("Directory" + file.getUri() + File.separator + lastSegment + " could not be created.");
        }

View on GitHub (pinned to 0152f468fc)

Solutions

1. Pass a concrete relative directory name without leading/trailing slashes, e.g. "foo/bar" instead of "/foo/bar/".
2. Strip leading/trailing File.separator from the input before calling createDirectories.
3. Validate that the trimmed name is non-empty and contains at least one non-separator character before calling.
4. Split the path yourself and call createDirectories per-level if you need root-relative handling.

Example fix

// before
path.createDirectories("/mydir/"); // IllegalArgumentException: Display name is empty
// after
String name = "/mydir/".replaceAll("^/+|/+$", "");
if (!name.isEmpty()) path.createDirectories(name);

String name = raw == null ? "" : raw.replaceAll("^"+File.separator+"+|"+File.separator+"+$", "");
if (name.isEmpty() || name.split(File.separator).length == 0) throw new IllegalArgumentException("Need at least one directory segment");

boolean isCreatableDirName(String n) { return n != null && !n.replaceAll("^/+|/+$", "").isEmpty(); }

try { path.createDirectories(name); } catch (IllegalArgumentException e) { log.warn("Rejecting empty dir name", e); }

When it happens

Trigger: Calling createDirectories with a name that sanitizes to only path separators, e.g. "/" or "//", so displayName.split(File.separator) produces zero usable segments.

Common situations: Building the directory name by joining path components with a separator and passing the result including a trailing/leading slash; concatenating an empty variable into a path string; passing a URI path portion instead of a display name.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Display name contains file separator.
• Couldn't find any writable Obb dir
• Could not delete the selected backups
• Data directory cannot be empty.
• Could not create package staging directory

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/c3d4f696690541a7. Report an issue: GitHub.