try (final TarArchiveOutputStream tos = new TarArchiveOutputStream(baos)) {
            final byte[] content = "Some content".getBytes();
            final TarArchiveEntry entry = new TarArchiveEntry("unknown.xyz");
            entry.setSize(content.length);
            tos.putArchiveEntry(entry);
            tos.write(content);
            tos.closeArchiveEntry();
        }