String s = "привет мир";
for (char c : s.toCharArray()) {
    int code = (int)c;
    System.out.format("%04X ", code);
}

043F 0440 0438 0432 0435 0442 0020 043C 0438 0440

String prContentFormatHex = "";
for (char c : prContent.toCharArray()) {
    int code = (int)c;
    prContentFormatHex += String.format("%04X ", code);
}