A school cafeteria is giving an electronic survey to its stu- dents to improve their lunch menu. Create an application that will use a two-dimensional array to hold counters for the survey (Fig. 17.31). You will also provide JRadioButtons for the students to select whether they like or dislike a particular food.

Question

a) Copying the template to your working directory. Copy the C:Examples Tutorial17ExercisesFoodSurvey directory to your C:SimplyJava directory.

b) Opening the template file. Open the FoodSurvey.java file in your text editor.

c) Declaring a two-dimensional int array. On lines 29-30, insert code to declare a two- dimensional int array named display, with 4 rows and 2 columns.

d) Declaring local variables. On line 105, in method addJButtonActionPerformed, set the text of displayJTextArea to "Food Like Dislike" for the header. Cre- ate a local int variable index. This variable should contain the index of the selected item in foodJComboBox.

e) Using a for loop to display the data. Insert a for statement that will loop through each row in the foodChoices array (0–3). In the body of the loop, append the appro- priate food to displayJTextArea. The counter variable of the for statement will be used as the index of the foodChoices array. Add the "
" escape sequence to displayJText

Answer 1

```
1 // FoodSurvey.java
2 // This application takes a survey of opinions on various foods.
3 import java.awt.*;
4 import java.awt.event.*;
5 import javax.swing.*;
6
7 public class FoodSurvey extends JFrame
8 {
9 // JComboBox to give choice of foods
10 private JComboBox foodJComboBox;
11
12 // JButton to add choice to JTextArea
13 private JButton addJButton;
14
15 // ButtonGroup to control like and dislike JRadioButtons
16 private ButtonGroup choiceButtonGroup;
17
18 // JRadioButtons to choose like or dislike food
19 private JRadioButton likeJRadioButton;
20 private JRadioButton dislikeJRadioButton;
21
22 // JTextArea to display results
23 private JTextArea displayJTextArea;
24
25 // String array for food choices
26 private String foodChoices[] = { "Pizza", "Hot Dog",
27 "Fish Sticks", "Mystery Meat" };
28
29 // two-dimensional array to store survey results
30 private int display[][] = new int[ 4 ][ 2 ];
31
32 // no-argument constructor
33 public FoodSurvey()
34 {
35 createUserInterface();
36 }
37
38 // create and position GUI components; register event handlers
39 private void createUserInterface()
40 {
41 // get content pane for attaching GUI components
42 Container contentPane = getContentPane();
43
44 // enable explicit positioning of GUI components
45 contentPane.setLayout( null );
46
47 // set up foodJComboBox
48 foodJComboBox = new JComboBox( foodChoices );
49 foodJComboBox.setBounds( 16, 16, 110, 23 );
50 contentPane.add( foodJComboBox );
51
52 // set up choiceButtonGroup
53 choiceButtonGroup = new ButtonGroup();
54
55 // set up likeJRadioButton
56 likeJRadioButton = new JRadioButton();
57 likeJRadioButton.setBounds( 135, 16, 60, 23 );
58 likeJRadioButton.setText( "Like" );
59 likeJRadioButton.setSelected( true );
60 choiceButtonGroup.add( likeJRadioButton );
61 contentPane.add( likeJRadioButton );
62
63 // set up dislikeJRadioButton
64 dislikeJRadioButton = new JRadioButton();
65 dislikeJRadioButton.setBounds( 195, 16, 70, 23 );
66 dislikeJRadioButton.setText( "Dislike" );
67 choiceButtonGroup.add( dislikeJRadioButton );
68 contentPane.add( dislikeJRadioButton );
69
70 // set up addJButton
71 addJButton = new JButton();
72 addJButton.setBounds( 265, 16, 67, 23 );
73 addJButton.setText( "Add" );
74 contentPane.add ( addJButton );
75 addJButton.addActionListener(
76
77 new ActionListener() // anonymous inner class
78 {
79 // event handler called when addJButton is clicked
80 public void actionPerformed( ActionEvent event )
81 {
82 addJButtonActionPerformed( event );
83 }
84
85 } // end anonymous inner class
86
87 ); // end call to addActionListener
88
89 // set up displayJTextArea
90 displayJTextArea = new JTextArea();
91 displayJTextArea.setBounds( 16, 55, 315, 93 );
92 displayJTextArea.setEditable( false );
93 contentPane.add( displayJTextArea );
94
95 // set properties of application’s window
96 setTitle( "Food Survey" ); // set title bar string
97 setSize( 355, 190 ); // set window size
98 setVisible( true ); // display window
99
100 } // end method createUserInterface
101
102 // calculate and display the student and class average
103 private void addJButtonActionPerformed( ActionEvent event )
104 {
105 // output header
106 displayJTextArea.setText( "Food\tLike\tDislike" );
107
108 // index of selected food
109 int index = foodJComboBox.getSelectedIndex();
110
111 // for loop to display 2-dimensional array
112 for ( int j = 0; j < 4; j++ )
113 {
114 // add food to output
115 displayJTextArea.append( "\n" + foodChoices[ j ] + "\t" );
116
117 // increment appropriate counter
118 if ( likeJRadioButton.isSelected() && index == j )
119 {
120 display[ j ][ 0 ]++;
121 }
122 else if ( dislikeJRadioButton.isSelected() && index == j )
123 {
124 display[ j ][ 1 ]++;
125 }
126
127 displayJTextArea.append( display[ j ][ k ] + "\t" );
128
129
130
131 }
132
133 // end for
134
135 } // end method addJButtonActionPerformed
136
137 // main
138 public
139 {
140 FoodSurvey application = new FoodSurvey();
141 application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
142
143 } // end method main
144
145 } // end
```