XWPFHeaderFooterPolicy headerFooterPolicy = document.getHeaderFooterPolicy();
    XWPFHeaderFooter header = headerFooterPolicy.getDefaultHeader();
    XWPFParagraph paragraph = header.getListParagraph().iterator().next();

    if (!paragraph.getRuns().isEmpty()) {
        List<XWPFRun> runs = paragraph.getRuns();
        for (int i = 0; i < runs.size(); i++) {
            String oneparaString = runs.get(i).getDocument().getHeaderList().get(i).getText();
             System.out.println(oneparaString);
            for (Map.Entry<String, String> entry : mapa.entrySet()) {
                oneparaString = oneparaString.replace(entry.getKey(),
                        entry.getValue());
            }

            runs.get(i).setText(oneparaString,0);
        }
    }