how to remove comma if string having comma at end

if (names.endsWith(",")) {
    names = names.substring(0, names.length()-1);
}

int last = names.length() - 1;
if (last > 0 && names.charAt(last) == ',') {
    names = names.substring(0, last);
}

You could try a regular expression:

names = names.replaceAll(",$", "");

Or a simple substring:

if (names.endsWith(",")) {
  names = names.substring(0, names.length() - 1);
}