Hello,

I am getting the following errors:

unexpected type line 433
operator + cannot be applied to <any>,double line 433
operator + cannot be applied to <nulltype>,double line 433
incompatible types line 433
unexpected type line 441

In the below file. I know its probably something simple, but could use a fresh pair of eyeballs. Thanks in advance!

import javax.swing.*;           //Needed for Swing classes
import java.awt.*;              //Needed for GUI applications
import java.awt.event.*;        //Needed for ActionListener Interface
import java.text.DecimalFormat; //Needed for formatting decimal numbers


//Create a class called TravelExpenses that inherits from JFrame.
public class TravelExpenses extends JFrame
{
	  private JPanel panelNorth;																		
	  private JLabel messageLabelGreeting; 															
	  private JPanel panelCenter;
	  private JLabel messageLabelNumDays;															    
	  private JLabel messageLabelAirfare;																
	  private JLabel messageLabelRental;															
	  private JLabel messageLabelMiles;															
	  private JLabel messageLabelParking;																
	  private JLabel messageLabelTaxi;																
	  private JLabel messageLabelRegistration;														
	  private JLabel messageLabelLodging;																
	  private JTextField numDaysTextField;																
	  private JTextField airfareTextField;															
	  private JTextField rentalTextField;																	
	  private JTextField milesTextField;																	
	  private JTextField parkingTextField;																
	  private JTextField taxiTextField;																	
	  private JTextField registrationTextField;															
	  private JTextField lodgingTextField;																
	  private JPanel panelSouth;																		
	  private JButton calcButton; 																	    
	  private final int WINDOW_WIDTH = 500; 																	
	  private final int WINDOW_HEIGHT = 500;
	  
	/*
    Constructor +TravelExpenses()
   */
   public TravelExpenses()
   {
   		//Set the title of the window to Travel Expense Calculator.
	setTitle("Travel Expense Calculator");	
		
	//Set the size of the window using the constants.
	setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
	
	//Specify what happens when the close button is clicked.
	setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	
	//Get the content pane of the JFrame and set the layout manager to border layout.
	getContentPane().setLayout(new BorderLayout());
	
	//Create a greeting label that contains the message “This program will calculate your travel expenses!”
	messageLabelGreeting = new JLabel("This program will calculate your travel expenses!");
	
	//Create the north panel.
	panelNorth = new JPanel();
	
	//Add the label to the north panel.
	panelNorth.add(messageLabelGreeting);
	
	//Add north panel to the content frame.
	add(panelNorth, BorderLayout.NORTH);
	
	//Create labels that direct the user to enter the required information.
	messageLabelNumDays = new JLabel("Enter the number of days you traveled:");															    
	messageLabelAirfare = new JLabel("Enter the amount of your airfare, without dollar sign or commas.  If none, enter 0:");																
	messageLabelRental = new JLabel("Enter the daily rate of your rental car, without dollar sign or commas.  If none, " +
						  			"enter 0:");															
	messageLabelMiles = new JLabel("Enter the number of miles you drove daily in your private vehicle.  If none, enter 0:");															
	messageLabelParking = new JLabel("Enter the daily rate of parking fees you paid, without dollar sign or commas.  " +
									 "If none, enter 0:");																
	messageLabelTaxi = new JLabel("Enter the daily rate of taxi fees you paid, without dollar sign or commas.  " +
								  "If none, enter 0:");																
	messageLabelRegistration = new JLabel("Enter any seminar or conference registration fees you paid, without dollar " +
										  "sign or commas.  If none, enter 0:");														
	messageLabelLodging = new JLabel("Enter the per night rate of lodging you paid, without dollar sign or commas:");
	
	//Create text fields to recieve user input.
	numDaysTextField = new JTextField(10);																
	airfareTextField = new JTextField(10);															
	rentalTextField = new JTextField(10);																	
	milesTextField = new JTextField(10);																	
	parkingTextField = new JTextField(10);																
	taxiTextField = new JTextField(10);																	
	registrationTextField = new JTextField(10);															
	lodgingTextField = new JTextField(10);
	
	//Create the center panel.
	panelCenter = new JPanel();
	
	//Add all labels and text fields to center panel.
	panelCenter.add(messageLabelNumDays);
	panelCenter.add(messageLabelAirfare);	
	panelCenter.add(messageLabelRental);
	panelCenter.add(messageLabelMiles);
	panelCenter.add(messageLabelParking);
	panelCenter.add(messageLabelTaxi);
	panelCenter.add(messageLabelRegistration);
	panelCenter.add(messageLabelLodging);
	panelCenter.add(numDaysTextField);
	panelCenter.add(airfareTextField);
	panelCenter.add(rentalTextField);
	panelCenter.add(milesTextField);
	panelCenter.add(parkingTextField);
	panelCenter.add(taxiTextField);
	panelCenter.add(registrationTextField);
	panelCenter.add(lodgingTextField);
	
	//Add center panel to content frame.
	add(panelCenter, BorderLayout.CENTER);
	
	//Create a button with the caption "Calculate".
	calcButton = new JButton("Calculate");
	
	//Add button listener that implements action listener for this button.
	calcButton.addActionListener(new CalcButtonListener());
	
	//Create the south panel.
	panelSouth = new JPanel();
	
	//Add button to the south panel.
	panelSouth.add(calcButton);
	
	//Add south panel to content frame.
	add(panelSouth, BorderLayout.SOUTH);
	
	//Display the window.
	setVisible(true);	
   
   }//end constructor
   
   //Write a private inner class called CalcButtonListener that implements ActionListener.
   /**
    CalcButtonListener is an action listener class for the Calculate button.
    */
    private class CalcButtonListener implements ActionListener
    {
    	/**
    	 The actionPerformed method	executes when the user clicks the Calculate button.
    	 @param e the event object
    	*/
    	public void actionPerformed(ActionEvent e)
    	{
    		//Variables
    		String input;                             //To hold user input
    		double numDays;                           //Number of days traveled.  Must be at least 1
			double airfare;                           //Amount of airfare.   Must be at least 0
			double rentalFees;  		              //Amount of rental car fees.  Must be at least 0
			double milesDriven;  		              //Amount of miles driven in personal vehicle.  Must be at least 0
			double parkingFees;  		              //Amount of parking fees.  Must be at least 0
			double taxiCharges;  		              //Amount of taxi charges.  Must be at least 0
			double registrationFees;  	              //Amount of conference or seminar registration fees.  Must be at least 0
			double lodgingCharges;  	              //Amount of lodging charges.  Must be at least 1
			double totalExpenses;                     //Total amount of travel expenditures.
			double milesDrivenAllowableExpense;  	  //Total amount of gas money allowable to be reimbursed.
			double mealsAllowableExpense = 37;        //Total amount of meals allowable to be reimbursed. 
			double parkingAllowableExpense = 10;      //Total amount of parking fees allowable to be reimbursed.
			double taxiAllowableExpense = 20;         //Total amount of taxi fees allowable to be reimbursed.
			double lodgingAllowableExpense = 95;      //Total amount of lodging fees allowable to be reimbursed.
			double totalAllowableExpenses;            //Total amount that can be reimbursed.
			double expenseDifference;		          //Difference between travel expenditures and total amount that can be 
												      //reimbursed
												 
			/*
			 Get text entered by user in all text fields and convert values to doubles.  User will enter 0 if they did not 
			 incur expense.  User will not be allowed to enter negative numbers.  User must enter a value of > 1 for numDays 
			 and lodgingCharges.
			*/
			input = numDaysTextField.getText();
			numDays = Double.parseDouble(input);
			input = airfareTextField.getText();
			airfare = Double.parseDouble(input);
			input = rentalTextField.getText();
			rentalFees = Double.parseDouble(input);
			input = milesTextField.getText();
			milesDriven = Double.parseDouble(input);
			input = parkingTextField.getText();
			parkingFees = Double.parseDouble(input);
			input = taxiTextField.getText();
			taxiCharges = Double.parseDouble(input);
			input = registrationTextField.getText();
			registrationFees = Double.parseDouble(input);
			input = lodgingTextField.getText();
			lodgingCharges = Double.parseDouble(input);
			
			//While loop to validate numDays input is greater than 0.
			while (numDays <= 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "The number of days you traveled must be greater than 0!  " + 
    												"Try again.");
    			numDays = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate airfare input is not a negative number.
			while (airfare < 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "Airfare cannot be a negative number!  Try again.");
    			airfare = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate rentalFees input is not a negative number.
			while (rentalFees < 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "Rental fees cannot be a negative number!  Try again.");
    			rentalFees = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate milesDriven input is not a negative number.
			while (milesDriven < 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "The miles you drove cannot be a negative number!  Try again.");
    			milesDriven = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate parkingFees input is not a negative number.
			while (parkingFees < 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "Your parking fee cannot be a negative number!  Try again.");
    			parkingFees = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate taxiCharges input is not a negative number.
			while (taxiCharges < 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "Your taxi charges cannot be a negative number!  Try again.");
    			taxiCharges = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate registrationFees input is not a negative number.
			while (registrationFees < 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "Your registration fees cannot be a negative number!  Try again.");
    			registrationFees = Double.parseDouble(input);    		
    			
    		}//end while loop
    		
    		//While loop to validate lodgingCharges input is greater than 0.
			while (lodgingCharges <= 0)
    		{
    			//Dialog box to let the user know to try again.
    			input = JOptionPane.showInputDialog(null, "Your lodging fees must be greater than 0!  Try again.");
    			lodgingCharges = Double.parseDouble(input);    				  						
    			
    		}//end while loop
    		
    		//Calculate totalExpenses.
    		totalExpenses = (rentalFees + parkingFees + taxiCharges + lodgingCharges)(numDays) + registrationFees +  
    						airfare;
    						
    		//Calculate milesDrivenAllowableExpense.
    		milesDrivenAllowableExpense = milesDriven * .27;
    		
    		//Calculate totalAllowableExpenses.
    		totalAllowableExpenses = (milesDrivenAllowableExpense + mealsAllowableExpense + parkingAllowableExpense + 
    								 taxiAllowableExpense + lodgingAllowableExpense)(numDays);
    								 
    		//Calculate expenseDifference
    		expenseDifference = totalAllowableExpenses - totalExpenses;
				 	
			//Create decimal format object to format output.
			DecimalFormat rounder = new DecimalFormat("#0.00");	
				
			//Display total expenses incurred by the business person and the total allowable expenses for the trip.
			JOptionPane.showMessageDialog(null, "The total expense you incurred is $" + rounder.format(totalExpenses) + "." +
											    "\n" + "The total reimbursable expense is $" + 
											    rounder.format(totalAllowableExpenses) + ".");		
			
			//If totalExpenses is < totalAllowable expenses, display window showing the amount the user saved.
			if (totalExpenses < totalAllowableExpenses)
				JOptionPane.showMessageDialog(null, "You saved $" + rounder.format(expenseDifference) + "!"); 
					
			//If expenseDifference is > totalAllowable expenses, display window showing the amount the user owes.
			if (totalExpenses > totalAllowableExpenses)
				JOptionPane.showMessageDialog(null, "You owe $" + rounder.format(expenseDifference * -1) + "!");    		
    	
    	}//end actionPerformed method
    
    }//end CalcButtonListener private inner class   	
   
}//end class

It would help if you could someone make those error lines stand out a bit. Maybe a highlight or a comment or something. Do that, and I'll give it another look over.

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