Sequential Access Problem - Nothing is being written to file.

Question

Okay, quick introduction. I am a student and am in an intro Java class. I am understanding most of it; however, I am having one issue with an exercise that I am working on.
Here is the purpose:
To create a simple car reservation application that stores the reservation information in a sequential access file.
In the code what I need to happen is when the user clicks the Reserve Car button, the application needs to first check to see if there are cars already reserved for that day (there is a limit of 4 which is taken care of in the While statement). If the file content is null, it skips this while first.
If the content is null, then I need to open the file for writing, which is taken care of using FileWriter. The program is then to write the date information using the currentDate variable created before the while statement. Next, it is supposed to write the name entered and display a message box stating that the car has been reserved (which it does display).
However, I can add an infinate amount of reservations without getting the error message box stating that the max has been reached. So, I checked the reservations.txt file (which was intially created as a blank file) and I see that nothing at all is getting written to it. Here is the code, can anyone offer any insight into what I am missing. I am not getting any compliation or run-time errors, so I am sure this is just a simple problem I am overlooking. Thanks!
// This application allows users to input their names and
// reserve cars on various days.
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.Date;
import javax.swing.*;
import javax.swing.event.*;
public class CarReservation extends JFrame
   // JLabel and JSpinner to display date
   private JLabel selectDateJLabel;
   private JSpinner dateJSpinner;
   // JLabel and JTextField to display name
   private JLabel nameJLabel;
   private JTextField nameJTextField;
   // JButton to reserve car
   private JButton reserveCarJButton;
   // Printwriter to write to files
   private PrintWriter output;
   //BufferedReader to read data from file
   private BufferedReader input;
   // file user will select
   private File reserveFile;
   // no-argument constructor
   public CarReservation()
      createUserInterface();
   // create and position GUI components
   public void createUserInterface()
      // get content pane for attaching GUI components
      Container contentPane = getContentPane();
      // enable explicit positioning of GUI components
      contentPane.setLayout( null );
      // set up selectDateJLabel
      selectDateJLabel = new JLabel();
      selectDateJLabel.setBounds( 16, 16, 96, 23 );
      selectDateJLabel.setText( "Select the date:" );
      contentPane.add( selectDateJLabel );
      // set up dateJSpinner
      dateJSpinner = new JSpinner( new SpinnerDateModel() );
      dateJSpinner.setBounds( 16, 43, 250, 23 );
      dateJSpinner.setEditor( new JSpinner.DateEditor(
         dateJSpinner, "MM/dd/yyyy" ) );
      contentPane.add( dateJSpinner );
      dateJSpinner.addChangeListener(
         new ChangeListener() // anonymous inner class
            // event handler called when dateJSpinner is changed
            public void stateChanged( ChangeEvent event )
               dateJSpinnerChanged( event );
         } // end anonymous inner class
      ); // end call to addActionListener           
      // set up nameJLabel
      nameJLabel = new JLabel();
      nameJLabel.setBounds( 16, 70, 100, 23 );
      nameJLabel.setText( "Name: " );
      contentPane.add( nameJLabel );
      // set up nameJTextField
      nameJTextField = new JTextField();
      nameJTextField.setBounds( 16, 97, 250, 23 );
      contentPane.add( nameJTextField );
      // set up reserveCarJButton
      reserveCarJButton = new JButton();
      reserveCarJButton.setBounds( 16, 130, 250, 23 );
      reserveCarJButton.setText( "Reserve Car" );
      contentPane.add( reserveCarJButton );
      reserveCarJButton.addActionListener(
         new ActionListener() // anonymous inner class
            // event handler called when reserveCarJButton is clicked
            public void actionPerformed( ActionEvent event )
               reserveCarJButtonActionPerformed( event );
         } // end anonymous inner class
      ); // end call to addActionListener
      // set properties of application's window
      setTitle( "Car Reservation" ); // set title bar string
      setSize( 287, 190 );           // set window size
      setVisible( true );            // display window
   } // end method createUserInterface
   // write reservation to a file
   private void reserveCarJButtonActionPerformed( ActionEvent event )
   try
       // get file
       reserveFile = new File( "reservations.txt" );
       // open file
       FileReader currentFile = new FileReader( reserveFile );
       input = new BufferedReader( currentFile );
       // get date from dateJSpinner and format
       Date fullDate = ( Date ) dateJSpinner.getValue();
       String currentDate = fullDate.toString();
       String monthDay = currentDate.substring( 0 , 10 );
       String year = currentDate.substring( 24, 27 );
       currentDate = ( monthDay + " " + year );
       // declare variable to store number of people who reserve a car
       int dateCount = 1;
       // read a line from the file and store
       String contents = input.readLine();
       // while loop to read file data
       while ( contents != null )
           // if contents equal currentDate
           if ( contents.equals( currentDate ) )
               // check reservation number
               if ( dateCount <4 )
                   dateCount++;
               else
                   // display error message
                   JOptionPane.showMessageDialog( this,
                      "There are no more cars available for this day!",
                      "All Cars Reserved", JOptionPane.ERROR_MESSAGE );
                   // disable button
                   reserveCarJButton.setEnabled( false );
                   // exit the method
                   return;
               } // end else                
           } // end if
         // read next line of file
         contents = input.readLine();
       } // end while
       // close the file
       input.close();
       FileWriter outputFile = new FileWriter( reserveFile, true );
       output = new PrintWriter( outputFile );
       // write day to file
       output.println( currentDate );
       // write reserved name to file
       output.println( nameJTextField.getText() );
       // display message that car has been reserved
       JOptionPane.showMessageDialog( this, "Your car has been reserved",
               "Thank You", JOptionPane.INFORMATION_MESSAGE);
   } // end try
   catch ( IOException exception )
       JOptionPane.showMessageDialog( this, "Please make sure the file exists " +
               "and is of the right format.", "I/O Error",
               JOptionPane.ERROR_MESSAGE );
       // disable buttons
       dateJSpinner.setEnabled( false );
       reserveCarJButton.setEnabled( false );
   } // end catch
   // clear nameJTextField
   nameJTextField.setText( "" );
   } // end method reserveCarJButtonActionPerformed
   // enable reserveCarJButton
   private void dateJSpinnerChanged( ChangeEvent event )
      reserveCarJButton.setEnabled( true );
   } // end method dateJSpinnerChanged
   // main method
   public static void main( String[] args )
      CarReservation application = new CarReservation();
      application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
   } // end method main

Answer 1

Thank you. Sorry about all the code. I have never posted in this forum before and was unsure what all you needed.
This was the problem though. Right after I posted my question, I went back and looked at the code over again and realized that I left that part out! I added it in and it works perfectly. I came back to update my post but you had already answered it!
I really appreciate the quick response.
Mike