wrong attached file name in javax.mail

I have an Javax.mail application what receive e-mails and find a text in the attached pdf and docx. I the file name contains utf-8 characters it looks like: =?utf-8?Q?Sz=C3=A1mla.docx?= In the function it is come from: String fileName = part.getFileName();

private boolean findInAttachment(Message message, String filterText) throws MessagingException, IOException, Exception {
    boolean attachContains = false;

    if(message.getContentType().contains("multipart")) {
        Multipart multiPart = (Multipart) message.getContent();
        int numberOfParts = multiPart.getCount();

        for(int partCount = 0; partCount < numberOfParts; partCount++) {
            MimeBodyPart part = (MimeBodyPart) multiPart.getBodyPart(partCount);
            if(Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition())) {
                // this part is attachment
                String fileName = part.getFileName();
                String fullName = AnalyzeEmailsApp.getUserDir() + File.separator + fileName;

                if(isFileExtension(fileName, "docx")) {
                    part.saveFile(fullName);
                    attachContains = findInDocx(fullName, filterText);
                    DeleteAttachmentFile(fullName);
                } else if(isFileExtension(fileName, "pdf")) {
                    part.saveFile(fullName);
                    attachContains = findInPdf(fullName, filterText);
                    DeleteAttachmentFile(fullName);
                }
            } // if
        } // for
    } // if

    return attachContains;
}

How can I get the right file name (Számla.docx)?

you can use MimeUtility.decodeText() to decode the MIME encoded-word format.

import javax.mail.internet.MimeUtility;

String fileName = part.getFileName();
if (fileName != null) {
    fileName = MimeUtility.decodeText(fileName);
}

The =?utf-8?Q?Sz=C3=A1mla.docx?= is RFC 2047 encoded-word syntax. MimeUtility.decodeText() handles both Q-encoding (quoted-printable) and B-encoding (base64).

MimeBodyPart part = (MimeBodyPart) multiPart.getBodyPart(partCount);
if (Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition())) {
    String fileName = part.getFileName();
    if (fileName != null) {
        fileName = MimeUtility.decodeText(fileName);
    }
    String fullName = AnalyzeEmailsApp.getUserDir() + File.separator + fileName;
    // ... the rest
}