(Table of Powers Application) Write an application that displays a table of numbers from 1 to an upper limit, along with ethe square and cube each number. The user should specify the upper limit, and the results should be displayed in a JTextArea as in Fig. 8.23.

Question

```

a) Copying the template to your working directory. Copy the directory C:Examples Tutorial08ExercisesTableOfPowers to your C:SimplyJava directory.

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

c) Handling the keyPressed event for the Upper limit: JTextField. Add code to the limitJTextFieldKeyPressed event handler (which begins in line 97) to clear outputJTextArea.

d) Adding code to the Calculate JButton event handler. Add the code specified in steps e through j to the calculateJButtonActionPerformed event handler, which immediately follows the limitJTextFieldKeyPressed event handler.

e) Declaring a variable to store the loop counter. In the calculateJButtonAction- Performed event handler, declare int variable counter and initialize its value to 1.

f) Clearing outputJTextArea. Add a statement to calculateJButtonActionPer- formed that uses JTextArea method setText to clear any previous output in outputJTextAr

Answer 1

```
1 // Exercise 8.11: TableOfPowers.java
2 // Displays a table of powers up to a given limit.
3 import java.awt.*;
4 import java.awt.event.*;
5 import javax.swing.*;
6
7 public class TableOfPowers extends JFrame
8 {
9 // JLabel and JTextField for limit of loop counter
10 private JLabel limitJLabel;
11 private JTextField limitJTextField;
12
13 // JTextArea for displaying results
14 private JTextArea outputJTextArea;
15
16 // JButton to initiate calculations
17 private JButton calculateJButton;
18
19 // no-argument constructor
20 public TableOfPowers()
21 {
22 createUserInterface();
23 }
24
25 // create and position GUI components; register event handlers
26 private void createUserInterface()
27 {
28 // get content pane for attaching GUI components
29 Container contentPane = getContentPane();
30
31 // enable explicit positioning of GUI components
32 contentPane.setLayout( null );
33
34 // set up limitJLabel
35 limitJLabel = new JLabel();
36 limitJLabel.setBounds( 16, 16, 64, 26 );
37 limitJLabel.setText( "Upper limit:" );
38 contentPane.add( limitJLabel );
39
40 // set up limitJTextField
41 limitJTextField = new JTextField();
42 limitJTextField.setBounds( 85, 16, 59, 26 );
43 limitJTextField.setHorizontalAlignment( JTextField.RIGHT );
44 contentPane.add( limitJTextField );
45 limitJTextField.addKeyListener(
46
47 new KeyAdapter() // anonymous inner class
48 {
49 // event handler called if key pressed in limitJTextField
50 public void keyPressed( KeyEvent event )
51 {
52 limitJTextFieldKeyPressed( event );
53 }
54
55 } // end anonymous inner class
56
57 ); // end call to addKeyListener
58
59 // set up calculateJButton
60 calculateJButton = new JButton();
61 calculateJButton.setBounds( 166, 16, 130, 26 );
62 calculateJButton.setText( "Calculate" );
63 contentPane.add( calculateJButton );
64 calculateJButton.addActionListener(
65
66 new ActionListener() // anonymous inner class
67
68
69
70
71
72
73
74
75
76 );
77
78 //
79 outputJTextArea = new JTextArea();
80 outputJTextArea.setEditable( false );
81
82 // create JScrollPane that provides scrolling
83 // for outputJTextArea
84 JScrollPane scrollJScrollPane =
85 new JScrollPane( outputJTextArea );
86 scrollJScrollPane.setBounds( 16, 56, 280, 95 );
87 contentPane.add( scrollJScrollPane );
88
89 // set properties of application’s window
90 setTitle( "Table Of Powers" ); // set title bar text
91 setSize( 320, 195 ); // set window's size
92 setVisible( true ); // display window
93
94 } // end method createUserInterface
95
96 // method called when user presses key in limitJTextField
97 private void limitJTextFieldKeyPressed( KeyEvent event )
98 {
99 outputJTextArea.setText( "" ); // clear outputJTextArea
100 }
101
102 // method called when user clicks calculateJButton
103 private void calculateJButtonActionPerformed( ActionEvent event
104 {
105 int counter = 1;
106
107 // clear JTextArea outputJTextArea
108 outputJTextArea.setText ( "" );
109
110 // add header
111 outputJTextArea.append( "n\tn-squared\tn-cubed" );
112
113 // obtain upper limit
114 int limit = Integer.parseInt( limitJTextField.getText() );
115
116 // calculate and display square and cube of 1 to limit
117 while ( counter <= limit )
118 {
119 // display result
120 outputJTextArea.append ( "\n" + counter + "\t" +
121 counter * counter + "\t" + counter * counter * counter );
122
123 counter++; // increment counter
124 }
125
126 } // end method calculateJButtonActionPerformed
127
128 // main method
129 public static void main( String args[] )
130 {
131 TableOfPowers application = new TableOfPowers();
132 application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
133
134 } // end method main
135
136 } // end class TableOfPowers
```