how to delete string duplicate from an array list

basically I have a method that opens up a text file and adds all the strings to an array, but when I call it it, but it keeps adding the same strings over and over again, my question is how to delete any duplicate strings from ArrayList. verifiedMules is the arraylist.

    public void loadAccountsToList() throws IOException{
    String filepath = getDirectoryData() + "/MulesIGN.txt";
    try(Stream<String> stream = Files.lines(Paths.get(filepath))){
        stream.forEach(s ->{
            log("Added: '"+s+"'");