Create an application that allows a user to reserve a car for the specified day (Fig. 25.52). The car reservation company can rent out only four cars per day. Let the application allow the user to specify a certain day. If four cars have already been reserved for that day, then indicate to the user that no vehicles are available. Reserva- tions are stored in reservations.txt.

Question

a) Copying the template to your working directory. Copy the directory C:Examples Tutorial25ExercisesCarReservation to your C:SimplyJava directory.

b) Opening the template file. Open the CarReservation.java file in your text editor. c) Declaring a BufferedReader and a PrintWriter instance variable. At line 24,

declare two instance variables—a BufferedReader object named input, which will

be used to read from a file, and a PrintWriter object named output, which will be used to write to a file.

d) Opening a file to read from. In the reserveCarJButtonActionPerformed method (which immediately follows createUserInterface), create a new File object reserveFile for the file reservations.txt. Then, add a try block. Inside the try block, create a FileReader by passing the reserveFile to its constructor . Use this FileReader to initialize BufferedReader input.

e) Retrieving the selected date. For this application, you should store in reserva- tions.txt the date selected

Answer 1

```

1 // CarReservation.java
2 // This application allows users to input their names and
3 // reserve cars on various days.
4 import java.awt.*;
5 import java.awt.event.*;
6 import java.io.*;
7 import java.util.Date;
8 import javax.swing.*;
9 import javax.swing.event.*;
10
11 public class CarReservation extends JFrame
12 {
13 // JLabel and JSpinner to display date
14 private JLabel selectDateJLabel;
15 private JSpinner dateJSpinner;
16
17 // JLabel and JTextField to display name
18 private JLabel nameJLabel;
19 private JTextField nameJTextField;
20
21 // JButton to reserve car
22 private JButton reserveCarJButton;
23
24 // BufferedReader and PrintWriter to allow
25 // reading from, and writing to, a file
26 private BufferedReader input;
27 private PrintWriter output;
28
29 // no-argument constructor
30 public CarReservation()
31 {
32 createUserInterface();
33 }
34
35 // create and position GUI components
36 public void createUserInterface()
37 {
38 // get content pane for attaching GUI components
39 Container contentPane = getContentPane();
40
41 // enable explicit positioning of GUI components
42 contentPane.setLayout( null );
43
44 // set up selectDateJLabel
45 selectDateJLabel = new JLabel();
46 selectDateJLabel.setBounds( 16, 16, 96, 23 );
47 selectDateJLabel.setText( "Select the date:" );
48 contentPane.add( selectDateJLabel );
49
50 // set up dateJSpinner
51 dateJSpinner = new JSpinner( new SpinnerDateModel() );
52 dateJSpinner.setBounds( 16, 43, 250, 23 );
53 dateJSpinner.setEditor( new JSpinner.DateEditor(
54 dateJSpinner, "MM/dd/yyyy" ) );
55 contentPane.add( dateJSpinner );
56 dateJSpinner.addChangeListener(
57
58 new ChangeListener() // anonymous inner class
59 {
60 // event handler called when dateJSpinner is changed
61 public void stateChanged( ChangeEvent event )
62 {
63 dateJSpinnerChanged( event );
64 }
65
66 } // end anonymous inner class
67
68 ); // end call to addActionListener
69
70 // set up nameJLabel
71 nameJLabel = new JLabel();
72 nameJLabel.setBounds( 16, 70, 100, 23 );
73 nameJLabel.setText( "Name: " );
74 contentPane.add( nameJLabel );
75
76 // set up nameJTextField
77 nameJTextField = new JTextField();
78 nameJTextField.setBounds( 16, 97, 250, 23 );
79 contentPane.add( nameJTextField );
80
81 // set up reserveCarJButton
82 reserveCarJButton = new JButton();
83 reserveCarJButton.setBounds( 16, 130, 250, 23 );
84 reserveCarJButton.setText( "Reserve Car" );
85 contentPane.add( reserveCarJButton );
86 reserveCarJButton.addActionListener(
87
88 new ActionListener() // anonymous inner class
89 {
90 // event handler called when reserveCarJButton is clicked
91 public void actionPerformed( ActionEvent event )
92 {
93 reserveCarJButtonActionPerformed( event );
94 }
95
96 } // end anonymous inner class
97
98 ); // end call to addActionListener
99
100 // set properties of application's window
101 setTitle( "Car Reservation" ); // set title bar string
102 setSize( 287, 190 ); // set window size
103 setVisible( true ); // display window
104
105 } // end method createUserInterface
106
107 // write reservation to a file
108 private void reserveCarJButtonActionPerformed( ActionEvent event )
109 {
110 File reserveFile = new File( "reservations.txt" );
111
112 // read reservations from, and write a reservation to, a file
113 try
114 {
115 // create buffered reader to open and read text file
116 FileReader inputFile = new FileReader( reserveFile );
117 input = new BufferedReader( inputFile );
118
119 // get selected date
120 Date fullDate = ( Date ) dateJSpinner.getValue();
121 String currentDate = fullDate.toString();
122 String monthDay = currentDate.substring( 0, 10 );
123 String year = currentDate.substring( 24, 28 );
124 currentDate = monthDay + " " + year;
125
126 int dateCount = 1;
127 String contents = input.readLine();
128
129 // check if too many cars are reserved
130 while ( contents != null )
131 {
132 // check reservation date
133 if ( contents.equals( currentDate ) )
134 {
135 // check reservation number
136 if ( dateCount < 4 )
137 {
138 dateCount++;
139 }
140 else
141 {
101 setTitle( "Car Reservation" ); // set title bar string
102 setSize( 287, 190 ); // set window size
103 setVisible( true ); // display window
104
105 } // end method createUserInterface
106
107 // write reservation to a file
108 private void reserveCarJButtonActionPerformed( ActionEvent event )
109 {
110 File reserveFile = new File( "reservations.txt" );
111
112 // read reservations from, and write a reservation to, a file
113 try
114 {
115 // create buffered reader to open and read text file
116 FileReader inputFile = new FileReader( reserveFile );
117 input = new BufferedReader( inputFile );
118
119 // get selected date
120 Date fullDate = ( Date ) dateJSpinner.getValue();
121 String currentDate = fullDate.toString();
122 String monthDay = currentDate.substring( 0, 10 );
123 String year = currentDate.substring( 24, 28 );
124 currentDate = monthDay + " " + year;
125
126 int dateCount = 1;
127 String contents = input.readLine();
128
129 // check if too many cars are reserved
130 while ( contents != null )
131 {
132 // check reservation date
133 if ( contents.equals( currentDate ) )
134 {
135 // check reservation number
136 if ( dateCount < 4 )
137 {
138 dateCount++;
139 }
140 else
141 {
142 JOptionPane.showMessageDialog( this, "Too many " +
143 "cars have already been reserved for that day.",
144 "Sorry", JOptionPane.INFORMATION_MESSAGE );
145
146 // disable reserveCarJButton
147 reserveCarJButton.setEnabled( false );
148
149 return; // exit method
150 }
151
152 } // end if
153
154 contents = input.readLine(); // read next line
155
156 } // end while
157
158 input.close(); // close BufferedReader
159
160 // create PrintWriter to open and write text file
161 FileWriter outputFile = new FileWriter( reserveFile, true );
162 output = new PrintWriter( outputFile );
163
164 // write user input to file output.println
165 ( currentDate ); output.println(
166 nameJTextField.getText() );
167
168 JOptionPane.showMessageDialog( this,
169 "Your car has been reserved.", "Thank you",
170 JOptionPane.INFORMATION_MESSAGE );
171
172 output.close(); // close PrintWriter
173
174 } // end try
175 catch ( IOException exception )
176 {
177 JOptionPane.showMessageDialog( this, "Invalid file.",
178 "Error", JOptionPane.ERROR_MESSAGE );
179
180 // disable dateJSpinner and reserveCarJButton
181 dateJSpinner.setEnabled( false );
182 reserveCarJButton.setEnabled( false );
183 }
184
185 nameJTextField.setText( "" );
186
187 } // end method reserveCarJButtonActionPerformed
188
189 // enable reserveCarJButton
190 private void dateJSpinnerChanged( ChangeEvent event )
191 {
192 reserveCarJButton.setEnabled( true );
193
194 } // end method dateJSpinnerChanged
195
196 // main method
197 public static void main( String[] args )
198 {
199 CarReservation application = new CarReservation();
200 application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
201
202 } // end method main
203
204 } // end class CarReservation
```