Double cannot be converted to JTextField

Question

On lines, 139 - 146 the error "Double cannot be converted to JTextField" comes up. I understand that I need to change the name of the variable but I am unsure where to change it. I've attempted to change the names under CalcButtonListener but it created more errors. Thank you for your time and help!

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class TravelExpenses extends JFrame
{
    private JPanel panel;
    private JPanel buttonPanel;

    private JTextField numDays;
    private JTextField airfare;
    private JTextField carRent;
    private JTextField miles;
    private JTextField parking;
    private JTextField taxi;
    private JTextField reg;
    private JTextField lodge;

    private JButton calcButton;
    private JButton resetButton;


public TravelExpenses()
{
    setTitle("Travel Expenses");

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    buildPanel();

    buildButtonPanel();

    add(panel, BorderLayout.CENTER);
    add(buttonPanel, BorderLayout.SOUTH);

    pack();
    setVisible(true);
}

private void buildPanel()
{
    //labels for text fields
    JLabel numDaysLabel = new JLabel("Number of days of the trip:");
    JLabel airfareLabel = new JLabel("Amount of airfare:");
    JLabel carRentLabel = new JLabel("Amount of car rental:");
    JLabel milesLabel = new JLabel("Miles driven(if a private vehicle was used):");
    JLabel parkingLabel = new JLabel("Parking fees:");
    JLabel taxiLabel = new JLabel("Taxi fees:");
    JLabel regLabel = new JLabel("Conference registaration:");
    JLabel lodgeLabel = new JLabel("Lodging charges per night:");

    //text fields
     numDays = new JTextField(10);
     airfare = new JTextField(10);
     carRent = new JTextField(10);
     miles = new JTextField(10);
     parking = new JTextField(10);
     taxi = new JTextField(10);
     reg = new JTextField(10);
     lodge = new JTextField(10);

    //new panel
    panel = new JPanel();

    //layout manager
    panel.setLayout(new GridLayout( 10,8));

    //add labels and text fields
    panel.add(numDaysLabel);
    panel.add(numDays);
    panel.add(airfareLabel);
    panel.add(airfare);
    panel.add(carRentLabel);
    panel.add(carRent);
    panel.add(milesLabel);
    panel.add(miles);
    panel.add(parkingLabel);
    panel.add(parking);
    panel.add(taxiLabel);
    panel.add(taxi);
    panel.add(regLabel);
    panel.add(reg);
    panel.add(lodgeLabel);
    panel.add(lodge);

    //put border around panel
    panel.setBorder(BorderFactory.createEmptyBorder(10,10, 1, 10));

}

//method creates button panel
private void buildButtonPanel()
{
    //create button for calc
    calcButton = new CButton("Calculate");

    calcButton.addActionListener(new CalcButtonListener());

    resetButton = new JButton("Reset");

    resetButton.addActionListener(new ResetButtonListener());

    buttonPanel = new JPanel();
    buttonPanel.add(resetButton);
    buttonPanel.add(calcButton);
}
//listener for calc button
private class CalcButtonListener implements ActionListener
{
    double numDays;
    double airfare;
    double carRent;
    double miles;
    double parking;
    double taxi;
    double reg;
    double lodge;

    public void actionPerformed(Action e)
    {
        double total;
        String msg;

        //get data
        getData();

        //total
        total = determineTotal();

        msg = String.format("Total cost: $%,.2f\n", total);

        JOptionPane.showMessageDialog(null, msg);

    }
}

**Below is the chunk I am having issues with**
private void getData()
{
    numDays = Double.parseDouble(numDays.getText());
    airfare = Double.parseDouble(airfare.getText());
    carRent = Double.parseDouble(carRent.getText());
    miles = Double.parseDouble(miles.getText());
    parking = Double.parseDouble(parking.getText());
    taxi = Double.parseDouble(taxi.getText());
    reg = Double.parseDouble(reg.getText());
    lodge = Double.parseDouble(lodge.getText());    
}

Answer 1

On lines, 139 - 146 you are accessing members of TravelExpenses class rather than CalcButtonListener class.

Put getData() and determineTotal() method in CalcButtonListener class and use scope specifiers of particular member like for JtextField use: TravelExpenses.this.numDays as like for all JtextField.

Use below code for CalcButtonListener:

private class CalcButtonListener implements ActionListener
{
double numDays;
double airfare;
double carRent;
double miles;
double parking;
double taxi;
double reg;
double lodge;

public void actionPerformed(Action e)
{
    double total;
    String msg;

    //get data
    getData();

    //total
    total = determineTotal();

    msg = String.format("Total cost: $%,.2f\n", total);

    JOptionPane.showMessageDialog(null, msg);

}
private void getData()
{
    numDays = Double.parseDouble(TravelExpenses.this.numDays.getText());
    airfare = Double.parseDouble(TravelExpenses.this.airfare.getText());
    carRent = Double.parseDouble(TravelExpenses.this.carRent.getText());
    miles = Double.parseDouble(TravelExpenses.this.miles.getText());
    parking = Double.parseDouble(TravelExpenses.this.parking.getText());
    taxi = Double.parseDouble(TravelExpenses.this.taxi.getText());
    reg = Double.parseDouble(TravelExpenses.this.reg.getText());
    lodge = Double.parseDouble(TravelExpenses.this.lodge.getText());

}

private double determineTotal()
{
    double total = numDays * airfare * carRent * miles * parking * taxi * reg * lodge;

    return total;
}
}

Here you can find complete code.

    import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class TravelExpenses extends JFrame {
    private JPanel panel;
    private JPanel buttonPanel;

    private JTextField numDays;
    private JTextField airfare;
    private JTextField carRent;
    private JTextField miles;
    private JTextField parking;
    private JTextField taxi;
    private JTextField reg;
    private JTextField lodge;

    private JButton calcButton;
    private JButton resetButton;

    public TravelExpenses() {
        setTitle("Travel Expenses");

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        buildPanel();

        buildButtonPanel();

        add(panel, BorderLayout.CENTER);
        add(buttonPanel, BorderLayout.SOUTH);

        pack();
        setVisible(true);
    }

    private void buildPanel() {
        // labels for text fields
        JLabel numDaysLabel = new JLabel("Number of days of the trip:");
        JLabel airfareLabel = new JLabel("Amount of airfare:");
        JLabel carRentLabel = new JLabel("Amount of car rental:");
        JLabel milesLabel = new JLabel("Miles driven(if a private vehicle was used):");
        JLabel parkingLabel = new JLabel("Parking fees:");
        JLabel taxiLabel = new JLabel("Taxi fees:");
        JLabel regLabel = new JLabel("Conference registaration:");
        JLabel lodgeLabel = new JLabel("Lodging charges per night:");

        // text fields
        numDays = new JTextField(10);
        airfare = new JTextField(10);
        carRent = new JTextField(10);
        miles = new JTextField(10);
        parking = new JTextField(10);
        taxi = new JTextField(10);
        reg = new JTextField(10);
        lodge = new JTextField(10);

        // new panel
        panel = new JPanel();

        // layout manager
        panel.setLayout(new GridLayout(10, 8));

        // add labels and text fields
        panel.add(numDaysLabel);
        panel.add(numDays);
        panel.add(airfareLabel);
        panel.add(airfare);
        panel.add(carRentLabel);
        panel.add(carRent);
        panel.add(milesLabel);
        panel.add(miles);
        panel.add(parkingLabel);
        panel.add(parking);
        panel.add(taxiLabel);
        panel.add(taxi);
        panel.add(regLabel);
        panel.add(reg);
        panel.add(lodgeLabel);
        panel.add(lodge);

        // put border around panel
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 1, 10));

    }

//method creates button panel
    private void buildButtonPanel() {
        // create button for calc
        calcButton = new CButton("Calculate");

        calcButton.addActionListener(new CalcButtonListener());

        resetButton = new JButton("Reset");

        resetButton.addActionListener(new ResetButtonListener());

        buttonPanel = new JPanel();
        buttonPanel.add(resetButton);
        buttonPanel.add(calcButton);
    }

//listener for calc button
    private class CalcButtonListener implements ActionListener {
        double numDays;
        double airfare;
        double carRent;
        double miles;
        double parking;
        double taxi;
        double reg;
        double lodge;

        public void actionPerformed(ActionEvent e) {
            double total;
            String msg;

            // get data
            getData();

            // total
            total = determineTotal();

            msg = String.format("Total cost: $%,.2f\n", total);

            JOptionPane.showMessageDialog(null, msg);

        }

        private void getData() {
            numDays = Double.parseDouble(TravelExpenses.this.numDays.getText());
            airfare = Double.parseDouble(TravelExpenses.this.airfare.getText());
            carRent = Double.parseDouble(TravelExpenses.this.carRent.getText());
            miles = Double.parseDouble(TravelExpenses.this.miles.getText());
            parking = Double.parseDouble(TravelExpenses.this.parking.getText());
            taxi = Double.parseDouble(TravelExpenses.this.taxi.getText());
            reg = Double.parseDouble(TravelExpenses.this.reg.getText());
            lodge = Double.parseDouble(TravelExpenses.this.lodge.getText());

        }

        private double determineTotal() {
            double total = numDays * airfare * carRent * miles * parking * taxi * reg * lodge;

            return total;
        }
    }

    private class ResetButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            // reset text fields
            numDays.setText("0");
            airfare.setText("0");
            carRent.setText("0");
            miles.setText("0");
            parking.setText("0");
            taxi.setText("0");
            reg.setText("0");
            lodge.setText("0");

        }
    }

    public static void main(String[] args) {
        TravelExpenses gc = new TravelExpenses();
    }
}