Java ArrayList Check for same Input in a while loop

how can I check in an arraylist for the same String while ignoring cases? Sorry in advance, I'm new at Stackoverflow

ArrayList listednames = new ArrayList<>();

    while (true) {
        String entry = JOptionPane.showInputDialog("name:");
        if (entry == null) {
            break;
        }
        entry = entry.trim();

        if (entry.equalsIgnoreCase("stop")) {
            break;
        }
        if (entry.isEmpty()) {
            continue;
        }
        if (listednames.contains(entry)) { // .equalsIgnoreCase wont work with lists
            continue;
        }

        listednames.add(entry);
        Collections.sort(listednames);
        String namen = listednames.toString();
        namen = namen.substring(1, namen.length()-1);
        System.out.println(namen);
    }




}

}