Modify the application you developed in Exercise 10.11. to calculate the present value for a future value. Recall that to calculate the present investment you should use the formula:

where


p is the amount needed to achieve the future value


r is the annual interest rate (for example, 5 is equivalent to 5%)


n is the number of years


a is the future-value amount.





For example, if a customer wants to reach the financial goal of $15,000 over a period of 5 years when the interest rate is 6.6%, the customer would need to invest $10,896.96 as shown in Fig. 13.23. The years are to be entered with a JSpinner in the range from 0 to 30 in incre- ments of 5. Your application should clear the JTextArea if the values in any of the input components are modified. Your application should also provide the user with a Clear JBut- ton which will clear the JTextFields and JTextArea and reset the value in the JSpinner to the initial value (0).





) Copying the template to your work

```
1 // PresentValue.java
2 // Application that calculates how much money should be invested in
3 // order to achieve a certain financial goal.
4 import java.awt.*;
5 import java.awt.event.*;
6 import java.text.*;
7 import javax.swing.*;
8 import javax.swing.event.*;
9
10 public class PresentValue extends JFrame
11 {
12 // JLabel and JTextField for future value input
13 private JLabel futureValueJLabel;
14 private JTextField futureValueJTextField;
15
16 // JLabel and JTextField for interest rate input
17 private JLabel interestRateJLabel;
18 private JTextField interestRateJTextField;
19
20 // JLabel and JSpinner for number of years input
21 private JLabel yearsJLabel;
22 private JSpinner yearsJSpinner;
23
24 // JLabel and JTextArea for initial amounts
25 // needed to reach future value
26 private JLabel amountNeededJLabel;
27 private JTextArea amountNeededJTextArea;
28
29 // JButton calculates initial amounts needed
30 // to reach future value
31 private JButton calculateJButton;
32
33 // JButton to clear values
34 private JButton clearJButton;
35
36 // no-argument constructor
37 public PresentValue()
38 {
39 createUserInterface();
40 }
41
42 // create and position GUI components; register event handlers
43 private void createUserInterface()
44 {
45 // get content pane for attaching GUI components
46 Container contentPane = getContentPane();
47
48 // enable explicit positioning of GUI components
49 contentPane.setLayout( null );
50
51 // set up futureValueJLabel
52 futureValueJLabel = new JLabel();
53 futureValueJLabel.setBounds( 20, 25, 90, 20 );
54 futureValueJLabel.setText( "Future value:" );
55 contentPane.add( futureValueJLabel );
56
57 // set up futureValueJTextField
58 futureValueJTextField = new JTextField();
59 futureValueJTextField.setBounds( 130, 25, 100, 20 );
60 futureValueJTextField.setHorizontalAlignment(
61 JTextField.RIGHT );
62 contentPane.add( futureValueJTextField );
63 futureValueJTextField.addKeyListener(
64
65 new KeyAdapter() // anonymous inner class
66 {
67 // event handler called when
68 // futureValueJTextField is edited
69 public void keyPressed( KeyEvent event )
70 {
71 futureValueJTextFieldKeyPressed( event );
72 }
73
74 } // end anonymous inner class
75
76 ); // end call to addKeyListener
77
78 // set up interestRateJLabel
79 interestRateJLabel = new JLabel();
80 interestRateJLabel.setBounds( 20, 60, 90, 20 );
81 interestRateJLabel.setText( "Interest rate:" );
82 contentPane.add( interestRateJLabel );
83
84 // set up interestRateJTextField
85 interestRateJTextField = new JTextField();
86 interestRateJTextField.setBounds( 130, 60, 100, 20 );
87 interestRateJTextField.setHorizontalAlignment(
88 JTextField.RIGHT );
89 contentPane.add( interestRateJTextField );
90 interestRateJTextField.addKeyListener(
91
92 new KeyAdapter() // anonymous inner class
93 {
94 // event handler called when
95 // interestRateJTextField is edited
96 public void keyPressed( KeyEvent event )
97 {
98 interestRateJTextFieldKeyPressed( event );
99 }
100
101 } // end anonymous inner class
102
103 ); // end call to addKeyListener
104
105 // set up yearsJLabel
106 yearsJLabel = new JLabel();
107 yearsJLabel.setBounds( 20, 95, 80, 20 );
108 yearsJLabel.setText( "Years:" );
109 contentPane.add( yearsJLabel );
110
111 // set up yearsJSpinner
112 yearsJSpinner = new JSpinner(
113 new SpinnerNumberModel( 0, 0, 30, 5 ) );
114 yearsJSpinner.setBounds( 130, 95, 100, 20 );
115 contentPane.add( yearsJSpinner );
116 yearsJSpinner.addChangeListener(
117
118 new ChangeListener() // anonymous inner class
119 {
120 // event handler called when yearsJSpinner is changed
121 public void stateChanged( ChangeEvent event )
122 {
123
124 }
125 yearsJSpinnerStateChanged( event );
126 } // end anonymous inner class
127
128 ); // end call to addChangeListener
129
130 // set up resultJLabel
131 amountNeededJLabel = new JLabel();
132 amountNeededJLabel.setBounds( 20, 130, 150, 20 );
133 amountNeededJLabel.setText( "Annual amount needed:" );
134 contentPane.add( amountNeededJLabel );
135
136 // set up amountNeededJTextArea
137 amountNeededJTextArea = new JTextArea();
138 amountNeededJTextArea.setBounds( 20, 155, 320, 115 );
139 amountNeededJTextArea.setEditable( false );
140 contentPane.add( amountNeededJTextArea );
141
142 // set up calculateJButton
143 calculateJButton = new JButton();
144 calculateJButton.setBounds( 250, 25, 90, 20 );
145 calculateJButton.setText( "Calculate" );
146 contentPane.add( calculateJButton );
147 calculateJButton.addActionListener(
148
149 new ActionListener() // anonymous inner class
150 {
151 // event handler called when calculateJButton is pressed
152 public void actionPerformed( ActionEvent event )
153 {
154 calculateJButtonActionPerformed( event );
155 }
156
157 } // end anonymous inner class
158
159 ); // end call to addActionListener
160
161 clearJButton = new JButton();
162 clearJButton.setBounds( 250, 60, 90, 20 );
163 clearJButton.setText( "Clear" );
164 contentPane.add( clearJButton );
165 clearJButton.addActionListener(
166
167 new ActionListener() // anonymous inner class
168 {
169 // event handler called when clearJButton is pressed
170 public void actionPerformed( ActionEvent event )
171 {
172 clearJButtonActionPerformed( event );
173 }
174
175 } // end anonymous inner class
176
177
178
179
180
181
182
183
184 } // end method createUserInterface
185
186 // calculate and display amounts
187 private void calculateJButtonActionPerformed( ActionEvent event )
188 {
189 String futureValueText = futureValueJTextField.getText();
190 int futureValue = Integer.parseInt( futureValueText );
191 String rateText = interestRateJTextField.getText();
192 double rate = Double.parseDouble( rateText );
193
194 Integer integerObject = ( Integer ) yearsJSpinner.getValue();
195 int years = integerObject.intValue();
196
197 amountNeededJTextArea.setText( "Year\tInitial Deposit" );
198 DecimalFormat dollars = new DecimalFormat( "$0.00" );
199
200 // for loop calculates total amount
201 for ( int counter = 5; counter <= years; counter += 5 )
202 {
203 double amount = futureValue / Math.pow(
204 ( 1 + rate / 100 ), counter );
205 amountNeededJTextArea.append(
206 "\n" + counter + "\t" + dollars.format( amount ) );
207
208 } // end for
209
210 } // end method calculateJButtonActionPerformed
211
212 // clear the JTextArea
213 private void futureValueJTextFieldKeyPressed( KeyEvent event )
214 {
215 amountNeededJTextArea.setText( "" );
216
217 } // end method futureValueJTextFieldKeyPressed
218
219 // clear the JTextArea
220 private void interestRateJTextFieldKeyPressed( KeyEvent event )
221 {
222 amountNeededJTextArea.setText( "" );
223
224 } // end method interestRateJTextFieldKeyPressed
225
226 // clear the JTextArea
227 private void yearsJSpinnerStateChanged( ChangeEvent event )
228 {
229 amountNeededJTextArea.setText( "" );
230
231 } // end method yearsJSpinnerStateChanged
232
233 // clear components and display
234 private void clearJButtonActionPerformed( ActionEvent event )
235 {
236 // clear the JTextFields
237 futureValueJTextField.setText( "" );
238 interestRateJTextField.setText( "" );
239
240 // reset the value in the JSpinner
241 yearsJSpinner.setValue( new Integer(
242
243 // clear the JTextArea
244 amountNeededJTextArea.setText( "" );
245
246 } // end method clearJButtonActionPerformed
247
248 //
249 public static void main( String args[] )
250 {
251 PresentValue application = new PresentValue();
252 application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
253
254 } // end method main
255
256 } // end class PresentValue
```