(Simple Encryption Application) This application uses a simple technique to encrypt a number. Encryption is the process of modifying data so that only those intended to receive the data can undo the changes and view the original data. The user inputs in a JTextField the number to be encrypted—this is often called the “plain text” value. The application then multiplies the number by 7 and adds 5 to encrypt the original number—this new value is Tutorial 5 Enhancing the Inventory Application 75 often called the “cypher text” value. The application displays the encrypted number in an uneditable JTextField as shown in Fig. 5.32. A user who receives the encr

Question

a) Copying the template to your working directory. Copy the C:Examples Tutorial05ExercisesSimpleEncryption directory to your C:SimplyJava directory.

b) Opening the template file. Open the SimpleEncryption.java file in your text editor. c) Coding the encryptJButtonActionPerformed event handler. Scroll to the event

handler encryptJButtonActionPerformed (lines 98–101). Insert a statement that

gets the number in the enterJTextField, converts the number to an int and assigns the value to int variable plainText. Next, insert a statement that multiplies the number stored in variable plainText by 7 and adds 5, then stores the result in int variable cypherText. Finally, insert a statement that displays the value of cypher- Text in encryptedJTextField.

d) Clearing the result when a new value is input by the user. Locate the event handler enterJTextFieldKeyPressed (it appears immediately after the event handler encryptJButtonActionPerformed) in the template so

Answer 1

```
1 // SimpleEncryption.java
2 // Application that uses a simple formula to encrypt numbers.
3 import java.awt.*;
4 import java.awt.event.*;
5 import javax.swing.*;
6
7 public class SimpleEncryption extends JFrame
8 {
9 // JLabel and JTextField for entering number to encrypt
10 private JLabel enterJLabel;
11 private JTextField enterJTextField;
12
13 // JLabel and JTextField for displaying encrypted number
14 private JLabel encryptedJLabel;
15 private JTextField encryptedJTextField;
16
17 // JButton to initiate encryption
18 private JButton encryptJButton;
19
20 // no-argument constructor
21 public SimpleEncryption()
22 {
23 createUserInterface();
24 }
25
26 // create and position GUI components; register event handlers
27 private void createUserInterface()
28 {
29 // get content pane for attaching GUI components
30 Container contentPane = getContentPane();
31
32 // enable explicit positioning of GUI components
33 contentPane.setLayout( null );
34
35 // set up enterJLabel
36 enterJLabel = new JLabel();
37 enterJLabel.setText( "Enter number to encrypt:" );
38 enterJLabel.setBounds( 20, 20, 140, 20 );
39 contentPane.add( enterJLabel );
40
41 // set up enterJTextField
42 enterJTextField = new JTextField();
43 enterJTextField.setBounds( 180, 20, 50, 20 );
44 contentPane.add( enterJTextField );
45 enterJTextField.addKeyListener(
46
47 new KeyAdapter() // anonymous inner class
48 {
49 // called when key pressed in enterJTextField
50 public void keyPressed( KeyEvent event )
51 {
52 enterJTextFieldKeyPressed( event );
53 }
54
55 } // end anonymous inner class
56
57 ); // end call to addKeyListener
58
59 // set up encryptedJLabel
60 encryptedJLabel = new JLabel();
61 encryptedJLabel.setText( "Encrypted number:" );
62 encryptedJLabel.setBounds( 20, 50, 140, 20 );
63 contentPane.add( encryptedJLabel );
64
65 // set up encryptedJTextField
66 encryptedJTextField = new JTextField();
67 encryptedJTextField.setEditable( false );
68 encryptedJTextField.setBounds( 180, 50, 50, 20);
69 contentPane.add( encryptedJTextField );
70
71 // set up encryptJButton
72 encryptJButton = new JButton ();
73 encryptJButton.setText( "Encrypt" );
74 encryptJButton.setBounds( 250, 20, 80, 20 );
75 contentPane.add( encryptJButton );
76 encryptJButton.addActionListener(
77
78
79
80
81
82
83
84
85
86
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88
89
90
91
92
93
94
95 } // end method createUserInterface
96
97 // encrypt number input by user
98 private void encryptJButtonActionPerformed ( ActionEvent event )
99 {
100 // read input value from enterJTextField
101 int plainText = Integer.parseInt( enterJTextField.getText() );
102
103 // to encrypt, multiply plainText by 7 and add 5
104 int cypherText = plainText * 7 + 5;
105
106 // display cypherText
107 encryptedJTextField.setText( String.valueOf( cypherText ) );
108
109 } // end method encryptJButtonActionPerformed
110
111 // clear encryptedJTextField because the value is now invalid
112 private void enterJTextFieldKeyPressed( KeyEvent event )
113 {
114 encryptedJTextField.setText( "" ); // clear encryptedJTextField
115
116 } // end method enterJTextFieldKeyPressed
117
118 //
119 public static void main( String args[] )
120 {
121 SimpleEncryption application = new SimpleEncryption();
122 application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
123
124 } // end method main
125
126 } // end class SimpleEncryption
```