I'm using PDFBox to replace text, strange characters

Question

I'm using PDFBox to replace text in a template and there are characters (e.g. a simple J) that the tool recognizes as a special character. Any help to solve this problem?

public static PDDocument replaceText(PDDocument document, Map<String, String> mapVars) throws IOException {
    
    for (PDPage page : document.getPages()) {
        PDFStreamParser parser = new PDFStreamParser(page);
        parser.parse();
        List<?> tokens = parser.getTokens();

        for (int j = 0; j < tokens.size(); j++) {
            Object next = tokens.get(j);
            if (next instanceof Operator) {
                Operator op = (Operator) next;

                String pstring = "";
                int prej = 0;

               if (op.getName().equals("TJ")) {
                    COSArray previous = (COSArray) tokens.get(j - 1);
                    
                    for (int k = 0; k < previous.size(); k++) {
                        Object arrElement = previous.getObject(k);
                        if (arrElement instanceof COSString) {
                            COSString cosString = (COSString) arrElement;
                            String string = cosString.getString();

                            if (j == prej) {
                                pstring += string;
                            } else {
                                prej = j;
                                pstring = string;
                            }
                        }
                    }
                    
                    if (mapVars.containsKey(pstring.trim())) {
                        String replacement = mapVars.get(pstring.trim());
                        COSString sx = new COSString(replacement);
                        sx.setValue(replacement.getBytes());
                        previous.clear();
                        previous.add(0, sx);
                    }
                }
            }
        }
        PDStream updatedStream = new PDStream(document);
        OutputStream out = updatedStream.createOutputStream(COSName.FLATE_DECODE);
        ContentStreamWriter tokenWriter = new ContentStreamWriter(out);
        tokenWriter.writeTokens(tokens);
        out.close();
        page.setContents(updatedStream);
    }

    return document;
}