public class Database {

    private Connection          connection          = null;
    private PreparedStatement   preparedStatement   = null;
    private ResultSet           resultSet           = null;

    // Method for registering a new account. Credentials are added into the database.
    public void registerAccount(String username, String password, String ipAddress) {

        try {

            Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
            connection = DriverManager
            .getConnection("jdbc:derby:C:\DB;create=true;upgrade=true");
            String query = "INSERT INTO Users (username, password, ip_address) VALUES" + "(?,?,?)";
            preparedStatement = connection.prepareStatement(query);
            preparedStatement.setString(1, username);
            preparedStatement.setString(2, password);
            preparedStatement.setString(3, ipAddress);
            preparedStatement.executeUpdate();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            close();
        }

    }

    private void close() {

        try {

            if (resultSet != null) {
                resultSet.close();
            }
            if (preparedStatement != null) {
                preparedStatement.close();
            }
            if (connection != null) {
                connection.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

// Checks if credetials are correct.
public boolean checkLogin(String username, String password) {

    try {

        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
        connection = DriverManager
                .getConnection("jdbc:derby:C:\DB;create=true;upgrade=true");
        String query = "SELECT username, password from Users WHERE username = ? AND password = ?";
        preparedStatement = connection.prepareStatement(query);
        preparedStatement.setString(1, username);
        preparedStatement.setString(2, password);
        resultSet = preparedStatement.executeQuery();

        if (resultSet.next()) {
            String user = resultSet.getString("username");
            String pass = resultSet.getString("password");
            if (username.equalsIgnoreCase(user)) {
                if (password.equals(pass)) {
                    return true;
                }
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        close();
    }
    return false;
}