How to fetch all pdf file from all directories in my Android app

I want to know how to fetch all PDF files from internal storage. Files can be in any directory, like some in DCIM folders or some in Downloads folder, and so on and so forth.

Note: I am using Android Studio (language: Java).

You can use MediaStore to fetch all PDF Files ,this is an example how to get all your PDF files :

   protected ArrayList<String> getPdfList() {
    ArrayList<String> pdfList = new ArrayList<>();
    Uri collection;

    final String[] projection = new String[]{
            MediaStore.Files.FileColumns.DISPLAY_NAME,
            MediaStore.Files.FileColumns.DATE_ADDED,
            MediaStore.Files.FileColumns.DATA,
            MediaStore.Files.FileColumns.MIME_TYPE,
    };

    final String sortOrder = MediaStore.Files.FileColumns.DATE_ADDED + " DESC";

    final String selection = MediaStore.Files.FileColumns.MIME_TYPE + " = ?";

    final String mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension("pdf");
    final String[] selectionArgs = new String[]{mimeType};

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        collection = MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL);
    }else{
        collection = MediaStore.Files.getContentUri("external");
    }


    try (Cursor cursor = getContentResolver().query(collection, projection, selection, selectionArgs, sortOrder)) {
        assert cursor != null;

        if (cursor.moveToFirst()) {
            int columnData = cursor.getColumnIndex(MediaStore.Files.FileColumns.DATA);
            int columnName = cursor.getColumnIndex(MediaStore.Files.FileColumns.DISPLAY_NAME);
            do {
                pdfList.add((cursor.getString(columnData)));
                Log.d(TAG, "getPdf: " + cursor.getString(columnData));
                //you can get your pdf files
            } while (cursor.moveToNext());
        }
    }
    return pdfList;
}