public class DatabaseHandler {

    private String dbUrl;
    private String username;
    private String password;
    private String dbClass;
//Den nya arrayList nedan
    ArrayList<String> att = new ArrayList();

    public DatabaseHandler(String dbUrl, String username, String password) {
        this.dbUrl = dbUrl;
        this.username = username;
        this.password = password;
        this.dbClass = "com.mysql.jdbc.Driver";
    }

    //metod för att göra ett SELECT-kommando
    public void executeSelect(String query) {
        try {
            Class.forName(dbClass);
            try (Connection con = DriverManager.getConnection(dbUrl, username, password)) {
                Statement statement = con.createStatement();
                ResultSet rs = statement.executeQuery(query);
//                int i = 0;
                while (rs.next()) {
                    String a = rs.getString(1);
//här lägger du till att.add(a), detta sparar output av ditt select-kommando i ett tomt index.
                    att.add(a);
                    System.out.println(a);
                }

            }

        } catch (ClassNotFoundException | SQLException e) {
            Logger.getLogger(this.getClass().getName(), e.getMessage());
        }

    }