dude546546575 dude546546575 - 1 year ago 69
Java Question

JButton Won't Calculate Inputted Value (Java)

So I am doing an assignment for my class and now I am stuck. I want to calculate the inputted values but every time i press the button It won't do anything. the instructor did put instructions which I followed but I am missing something. So please try not to change the code I will post the instructions that i am stuck on after the code.

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package assignment.pkg16;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.NumberFormat;
public class Assignment16 extends JFrame implements ActionListener
Container content = this.getContentPane();

JTextField tfAmountBorrowed = new JTextField (15);
JTextField tfIR= new JTextField (15);
JTextField tfYearsToPay= new JTextField (15);

JLabel lblPayment = new JLabel("Monthly Payment");
JLabel lblTotCost = new JLabel("Total Cost");

JButton btnCalculate = new JButton("Calculate");
public Assignment16()
JLabel aBorrowed = new JLabel("Amount Borrowed");
content.add(aBorrowed , BorderLayout.EAST);
JLabel intrestRate= new JLabel("Interest Rate (EX. 7.5)");
content.add(intrestRate , BorderLayout.EAST);
JLabel yTp = new JLabel("Years To Pay");
content.add(yTp , BorderLayout.EAST);
content.add(btnCalculate, BorderLayout.SOUTH);

public void createWindow()
content.setLayout(new GridLayout(0, 2, 5, 5));
this.setTitle("First GUI App");
this.setSize(350, 300);

public void actionPerformed(ActionEvent ae)
String amountStr = tfAmountBorrowed.getText();
String intrestRateStr = tfIR.getText();
String yearsToPayStr = tfYearsToPay.getText();

Double amountDbl = new Double(amountStr);
Double intrestRateDbl = new Double(intrestRateStr);
Double yearsToPayDbl = new Double(yearsToPayStr);

double amount = amountDbl.doubleValue();
double intrestRate = intrestRateDbl.doubleValue();
double yearsToPay = yearsToPayDbl.doubleValue();

double intrestFormula = ( ( intrestRate/100 ) /12 );
double payment = ( 1 - ( Math.pow( 1 / (1+intrestRate) , yearsToPay * 12 ) ) );

NumberFormat fmt = NumberFormat.getCurrencyInstance();
lblPayment.setText("" + fmt.format(intrestFormula));
lblTotCost.setText( ""+ fmt.format(payment ) );

public static void main(String[] args) {
Assignment16 a16 = new Assignment16();



Convert the input. The input entered by the user is in textual form. Before you can do calculations however, you need to convert it to binary form. Because the HowMuch application deals with fractional numbers you should convert each entry to a double value.

Here are the steps required to convert a String like "123.45" into a floating point double value. For more in-depth information, make sure you read Learning Unit 8B, "Data-In & Data Out".

Create a local Double object for each of the String variables extracted in Step 5. Construct your Doubleobjects by passing each String to the appropriate constructor, like this:

Double amountDbl = new Double(amountStr);

where amountStr is one of the String variables initialized in Step 5. [Note that a Double variable is different than a double [little d] variable. A Double variable is an object, but it can't be used for arithmetic. A doublevariable is a primitive value.]

Create a primitive double local variable to match each of the Double objects created in the previous step. Initialize your double variables by sending your Double objects the doubleValue() message, like this:

double amount = amountDbl.doubleValue();

Step 8

Perform the calculations. Now that you've retreived the information from the user you'll need to manipulate that information to calculate the answers required by the problem.

Here's what you need to know to perform your calculations:

The formula to calculate a payment when the loan amount, interest rate, and term are all known is:

loan amount x interest rate
payment = ____________________________________

1 - (1 / (1 + interest rate))term * 12

When you perform your calculations you can use two of the numbers you obtained in the previous step--loan amount and loan term--without any further processing.

You need to modify the interest rate variable, however, before you can use it because the user expects a monthly rate and the user entered a yearly rate. In addition, the rate entered by the user needs to be converted to a decimal percentage.

Here's what you need to do:

Since the user entered the interest rate as 7.5, rather than .075, the first step is to divide the interest rate by 100 and store the result back in the interest rate variable. This is the actual yearly interest rate.

The formula above however, requires a monthly interest rate not a yearly one. Divide the interest rate calculated in the previous step, this time by 12, and store the result back in your interest rate variable.

Once the interest rate is squared away create a new double variable called payment and plug the rest of the variables into the formula shown above storing the result in payment. Since Java doesn't have an exponentiation operator you'll have to use the Math.pow() method to calculate the "bottom" part of the interest calculation like this:

(1 - (Math.pow(1/(1+rate), term * 12)))

Step 9

Display the output. To display the output send the setText() message to the JLabel objects you created in Step 3. One complication is that you have to convert your new binary answers back into Strings before they can be displayed.

Here's a summary of how to do that.

Create a new local NumberFormat object using the getCurrencyInstance() method.

Send your NumberFormat object the format() message. Pass the number you want formatted as an argument.

Save the formatted String obtained by calling the format() method, and pass it to the appropriate setText()method.

variable [computed in Step 8] for the first output label. For the total cost label, simply multiply the monthly payment by 12 and then multiply the result by the term to find the total cost. paymentFormat the

I already did all other steps correctly however the program doesn't work. So please help and thank you. =)

Plus an error poops up :

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1842)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)
at java.lang.Double.<init>(Double.java:608)
at assignment.pkg16.Assignment16.actionPerformed(Assignment16.java:59)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Answer Source

From what I found is you forgot to add lblPayment & lblTotCost to your content.

find this code snippet "add(tfYearsToPay);" then add add(lblPayment); & add(lblTotCost); right underneath "add(tfYearsToPay);" and just before when you add the button to the content.

content.add(btnCalculate, BorderLayout.SOUTH);

hit control + shift + f (should format but your keys may be different)

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