如何忽略在java中向mysql表添加重复的电话号码

public void registration() throws ClassNotFoundException, SQLException {
    System.out.println("Do you want to register to pay advance in online type yes or  no");
    boolean flag = false;
    Set <String> pNumber = new HashSet <String>();
    String input = scan.next();
    if (input.equalsIgnoreCase("Yes")) {
        System.out.println("Enter your name");
        String name = scan.next();
        System.out.println("Enter password");
        String pWord = scan.next();
        System.out.println("Re-enter password");
        String reEnter = scan.next();
        if (pWord.equals(reEnter)) {
            String confirm = reEnter;
            System.out.println("Your password created successfully");
            System.out.println("Enter your phone number");
            String phoneNumber = scan.next();
            Connection conn = null;
            PreparedStatement ps = null;
            ResultSet rs = null;
            conn = MansionDBConnect.getConnection();
            String queryTwo = "select phone_number from registration";
            ps = conn.prepareStatement(queryTwo);
            rs = ps.executeQuery();
            while (rs.next()) {
                pNumber.add(rs.getString(1));
                //System.out.println(rs.getString(1));
            }
            System.out.println(pNumber.size());
            for (int i = 0; i < pNumber.size(); i++) {
                if (pNumber.contains(phoneNumber)) {
                    System.out.println("Already number registered");
                    //pNumber.remove(phoneNumber);
                    System.out.println(pNumber);
                    flag = true;
                    break;
                }
            }
            if (pNumber.equals(phoneNumber)) {
                System.out.println("Already number registered");
            }
            String query = "insert into registration (username,password,phone_number)values(?,?,?)";
            ps = conn.prepareStatement(query);
            ps.setString(1, name);
            ps.setString(2, confirm);
            ps.setString(3, phoneNumber);
            ps.executeUpdate();
            System.out.println("Your record created successfully try login");
        } else {
            System.out.println("password mismatch found try again");
        }
    } else {
        System.out.println("For more details please call us");
    }
}

registration()如果已存在具有相同手机号码的用户，我会尝试忽略该用户。我能够找到它是否存在，但之后应该执行其余的代码。但是query一直在执行。应该添加什么条件？