mysql and java registration?

Question

MySQL

I wrote the code:

private Boolean checkLogin() throws SQLException {
        String query="SELECT COUNT(*) FROM testtable WHERE LOGIN=?";
        PreparedStatement preparedStatement = DB.connection.prepareStatement(query);
        preparedStatement.setString(1,clientSend.getLogin());
        preparedStatement.execute();
       
       
    }

It is necessary to find out if the string is in the database in the LOGIN column, then the method will return true otherwise
false, how to implement it?
And yes, how to substitute variables in queries in java without using questions.

Answer 1

private Boolean checkLogin() throws SQLException {
        String query="SELECT COUNT(*) FROM testtable WHERE LOGIN= :login";
        PreparedStatement preparedStatement = DB.connection.prepareStatement(query);
        preparedStatement.setString("login", clientSend.getLogin());
        ResultSet resultSet = preparedStatement.executeQuery();
        if (!resultSet.next()) throw new RuntimeException();

        int count = resultSet.getInt(1);
        return count == 1;
    }