class EmbeddedFiles
{
    /**
     * Constructor.
     */
    private EmbeddedFiles()
    {
    }

    /**
     * create the second sample document from the PDF file format specification.
     *
     * @param file The file to write the PDF to.
     *
     * @throws IOException If there is an error writing the data.
     */
    public void doIt( String file) throws IOException
    {<FILL_FUNCTION_BODY>}

    /**
     * This will create a hello world PDF document with an embedded file.
     * <br>
     * see usage() for commandline
     *
     * @param args Command line arguments.
     */
    public static void main(String[] args) throws IOException
    {
        EmbeddedFiles app = new EmbeddedFiles();
        if( args.length != 1 )
        {
            app.usage();
        }
        else
        {
            app.doIt( args[0] );
        }
    }

    /**
     * This will print out a message telling how to use this example.
     */
    private void usage()
    {
        System.err.println( "usage: " + this.getClass().getName() + " <output-file>" );
    }
}

        try (PDDocument doc = new PDDocument())
        {
            PDPage page = new PDPage();
            doc.addPage( page );
            PDFont font = new PDType1Font(FontName.HELVETICA_BOLD);

            try (PDPageContentStream contentStream = new PDPageContentStream(doc, page))
            {
                contentStream.beginText();
                contentStream.setFont( font, 12 );
                contentStream.newLineAtOffset(100, 700);
                contentStream.showText("Go to Document->File Attachments to View Embedded Files");
                contentStream.endText();
            }

            //embedded files are stored in a named tree
            PDEmbeddedFilesNameTreeNode efTree = new PDEmbeddedFilesNameTreeNode();

            //first create the file specification, which holds the embedded file
            PDComplexFileSpecification fs = new PDComplexFileSpecification();

            // use both methods for backwards, cross-platform and cross-language compatibility.
            fs.setFile( "Test.txt" );
            fs.setFileUnicode("Test.txt");

            //create a dummy file stream, this would probably normally be a FileInputStream
            byte[] data = "This is the contents of the embedded file".getBytes(StandardCharsets.ISO_8859_1);
            ByteArrayInputStream fakeFile = new ByteArrayInputStream(data);
            PDEmbeddedFile ef = new PDEmbeddedFile(doc, fakeFile );
            //now lets some of the optional parameters
            ef.setSubtype( "text/plain" );
            ef.setSize( data.length );
            ef.setCreationDate( new GregorianCalendar() );

            // use both methods for backwards, cross-platform and cross-language compatibility.
            fs.setEmbeddedFile( ef );
            fs.setEmbeddedFileUnicode(ef);
            fs.setFileDescription("Very interesting file");

            // create a new tree node and add the embedded file
            PDEmbeddedFilesNameTreeNode treeNode = new PDEmbeddedFilesNameTreeNode();
            treeNode.setNames( Collections.singletonMap( "My first attachment",  fs ) );
            // add the new node as kid to the root node
            List<PDEmbeddedFilesNameTreeNode> kids = new ArrayList<>();
            kids.add(treeNode);
            efTree.setKids(kids);
            // add the tree to the document catalog
            PDDocumentNameDictionary names = new PDDocumentNameDictionary( doc.getDocumentCatalog() );
            names.setEmbeddedFiles( efTree );
            doc.getDocumentCatalog().setNames( names );

            // show attachments panel in some viewers 
            doc.getDocumentCatalog().setPageMode(PageMode.USE_ATTACHMENTS);

            doc.save( file );
        }
    
<no_super_class>