class PDFMerger implements Callable<Integer>
{
    // Expected for CLI app to write to System.out/System.err
    @SuppressWarnings("squid:S106")
    private final PrintStream SYSERR;

    @Option(names = {"-i", "--input"}, description = "the PDF files to merge.", paramLabel = "<infile>", required = true)
    private File[] infiles;

    @Option(names = {"-o", "--output"}, description = "the merged PDF file.", required = true)
    private File outfile;

    /**
     * Constructor.
     */
    public PDFMerger()
    {
        SYSERR = System.err;
    }

    /**
     * Infamous main method.
     *
     * @param args Command line arguments, should be at least 3.
     */
    public static void main( String[] args )
    {<FILL_FUNCTION_BODY>}

    public Integer call()
    {
        PDFMergerUtility merger = new PDFMergerUtility();

        try
        {
            for (File infile : infiles)
            {
                merger.addSource(infile);
            }

            merger.setDestinationFileName(outfile.getAbsolutePath());
            merger.mergeDocuments(IOUtils.createMemoryOnlyStreamCache());
        }
        catch (IOException ioe)
        {
            SYSERR.println( "Error merging documents [" + ioe.getClass().getSimpleName() + "]: " + ioe.getMessage());
            return 4;
        }
        return 0;
    }
}

        // suppress the Dock icon on OS X
        System.setProperty("apple.awt.UIElement", "true");

        int exitCode = new CommandLine(new PDFMerger()).execute(args);
        System.exit(exitCode);
    
<no_super_class>