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Java AWT controls issue

I'd like to create a calculator using Java AWT library, however I'm having problems putting a label and a textfield on the same row. Also, everything is mixing up. When I run the program, at first it shows 2 labels and 2 textfields on the same row, but if I resize it, the labels, buttons & textfields are one on top of another. Could you please help me?
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class Calculator extends Frame {
public static void main(String[] args) {
Frame frame= new Frame();
frame.setTitle("Mini Calculator App");
frame.setVisible(true);
frame.setSize(300,300);
LayoutManager gridBagLayout = new GridBagLayout();
frame.setLayout(gridBagLayout);
Label firstNumber = new Label("Add a number");
frame.add(firstNumber);
TextField numar1 = new TextField();
frame.add(numar1);
Label secondNumber = new Label("Add another number");
frame.add(secondNumber);
TextField numar2 = new TextField();
frame.add(numar2);
Choice operatie = new Choice();
operatie.add("+"); operatie.add("-");
operatie.add("*"); operatie.add("/");
frame.add(operatie);
Button calcul = new Button("Calculate");
frame.add(calcul);
Label result = new Label("Result is");
frame.add(result);
GridBagConstraints afisare;
afisare = new GridBagConstraints();
afisare.gridx = 0;
afisare.gridy = 0;
frame.add(firstNumber, afisare);
afisare = new GridBagConstraints();
afisare.gridx = 0;
afisare.gridy = 1;
afisare.gridwidth = 10;
afisare.gridheight = 10;
frame.add(numar1, afisare);
afisare = new GridBagConstraints();
afisare.gridx = 1;
afisare.gridy = 0;
frame.add(secondNumber, afisare);
afisare = new GridBagConstraints();
afisare.gridx = 1;
afisare.gridy = 1;
frame.add(numar2, afisare);
afisare = new GridBagConstraints();
afisare.gridx = 2;
afisare.gridy = 1;
frame.add(operatie, afisare);
afisare = new GridBagConstraints();
afisare.gridx = 4;
afisare.gridy = 0;
frame.add(result, afisare);
frame.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
}
}
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java.lang.numberformatexception empty string java awt

public class CustomCalculator extends Frame implements ActionListener{
Panel jp1 = new Panel();
Panel jp2 = new Panel();
Panel jp3 = new Panel();
Panel jp4 = new Panel();
Panel jp5 = new Panel();
Panel center_merge = new Panel();
Label l2 = new Label("Quantity : ");
TextField l2a = new TextField(20);
Label l3 = new Label("Invoice Value : ");
TextField l3a = new TextField(20);
Label l4 = new Label("Exchange Rate : ");
TextField l4a = new TextField(20);
Label l5 = new Label("Costing(A) : ");
TextField l5a = new TextField();
Label l6 = new Label("(A + 1%)(B) : ");
Label l6a = new Label();
Label l7 = new Label("BCD (C) : ");
Label l7a = new Label("");
Label l8 = new Label("CVD (D) : ");
Label l8a = new Label("");
Label l9 = new Label("Custom Education Cess (E) : ");
Label l9a = new Label("");
Label l10 = new Label("Custom Sec & Higher Edu.Cess (F) : ");
Label l10a = new Label("");
Label l11 = new Label("Additional Duty Imports (G) : ");
Label l11a = new Label("");
Label l12 = new Label("Total (H) : ");
Label l12a = new Label("");
Label l13 = new Label("Costing+Total (I) : ");
Label l13a = new Label("");
Label l14 = new Label("(H/Quantity) (J) : ");
Label l14a = new Label("");
Label l15 = new Label("4% SAD (G/Quantity) (K) : ");
Label l15a = new Label("");
Label l16 = new Label("Net Costing (L) : ");
Label l16a = new Label("");
Label l17 = new Label("Transportation (M) : ");
TextField l17a = new TextField(5);
Label l18 = new Label("Godown Rate (N) : ");
TextField l18a = new TextField(5);
Label l19 = new Label("Brokerage (O) : ");
TextField l19a = new TextField(5);
Label l20 = new Label("Actual Costing (P) : ");
Label l20a = new Label("");
Label l21 = new Label("Small Gatepass (Q) : ");
Label l21a = new Label("");
Label l22 = new Label("Big Gatepass (R) : ");
Label l22a = new Label("");
Button l2b = new Button("reset");
Button l3b = new Button("reset");
Button l4b = new Button("reset");
Button master_reset = new Button("reset all");
Button calc = new Button("Calculate");
public CustomCalculator()
{
super("Custom Calculator");
this.setSize(800,700);
jp1.setLayout(new FlowLayout());
//jp1.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp1.add(l2);
jp1.add(l2a);
jp1.add(l2b);
jp1.add(l3);
jp1.add(l3a);
jp1.add(l3b);
jp1.add(l4);
jp1.add(l4a);
jp1.add(l4b);
jp2.setLayout(new GridLayout(6,2));
//jp2.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp2.add(l5);
jp2.add(l5a);
jp2.add(l6);
jp2.add(l6a);
jp2.add(l7);
jp2.add(l7a);
jp2.add(l8);
jp2.add(l8a);
jp2.add(l9);
jp2.add(l9a);
jp2.add(l10);
jp2.add(l10a);
jp3.setLayout(new GridLayout(6,2));
//jp3.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp3.add(l11);
jp3.add(l11a);
jp3.add(l12);
jp3.add(l12a);
jp3.add(l13);
jp3.add(l13a);
jp3.add(l14);
jp3.add(l14a);
jp3.add(l15);
jp3.add(l15a);
jp3.add(l16);
jp3.add(l16a);
jp4.setLayout(new GridLayout(6,2));
//jp4.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp4.add(l17);
jp4.add(l17a);
jp4.add(l18);
jp4.add(l18a);
jp4.add(l19);
jp4.add(l19a);
jp4.add(l20);
jp4.add(l20a);
jp4.add(l21);
jp4.add(l21a);
jp4.add(l22);
jp4.add(l22a);
center_merge.setLayout(new GridLayout(1,3));
//center_merge.setBorder(BorderFactory.createLineBorder(Color.GRAY));
center_merge.add(jp2);
center_merge.add(jp3);
center_merge.add(jp4);
jp5.setLayout(new FlowLayout());
//jp5.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp5.add(calc);
jp5.add(master_reset);
this.setLayout(new BorderLayout());
this.add(jp1,BorderLayout.NORTH);
this.add(center_merge,BorderLayout.CENTER);
this.add(jp5,BorderLayout.SOUTH);
this.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent we)
{
System.exit(0);
}
});
l2b.addActionListener(this);
l3b.addActionListener(this);
l4b.addActionListener(this);
calc.addActionListener(this);
master_reset.addActionListener(this);
this.setVisible(true);
}
public static void main(String[] args) {
new CustomCalculator();
}
#Override
public void actionPerformed(ActionEvent ae) {
double quantity = 0;
double invoice_value = 0;
double exchange_rate = 0;
double A=0;
double B=0;
double C=0;
double D=0;
double E=0;
double F=0;
double G=0;
double H=0;
double I=0;
double J=0;
double K=0;
double L=0;
double M = 0;
double N = 0;
double O=0;
double P=0;
double Q=0;
double R=0;
try
{
quantity = Double.parseDouble(l2a.getText());
invoice_value = Double.parseDouble(l3a.getText());
exchange_rate = Double.parseDouble(l4a.getText());
M = Double.parseDouble(l17a.getText());
N = Double.parseDouble(l18a.getText());
O = Double.parseDouble(l19a.getText());
A = invoice_value*exchange_rate;
B = A+(0.01*A);
C = 0.075*B;
D = 0.12*(B+C);
E = 0.02*(C+D);
F = 0.01*(C+D);
G = 0.04*(B+C+D+E+F);
H = C+D+E+F+G;
I = A+H;
J = H/quantity;
K = G/quantity;
L = J-K;
P = L+M+N+O;
Q = (0.12*B)/quantity;
R = Q+K;
if(ae.getActionCommand().equals("calc"))
{
l5a.setText(String.valueOf(A));
l6a.setText(String.valueOf(B));
l7a.setText(String.valueOf(C));
l8a.setText(String.valueOf(D));
l9a.setText(String.valueOf(E));
l10a.setText(String.valueOf(F));
l11a.setText(String.valueOf(G));
l12a.setText(String.valueOf(H));
l13a.setText(String.valueOf(I));
l14a.setText(String.valueOf(J));
l15a.setText(String.valueOf(K));
l16a.setText(String.valueOf(L));
l20a.setText(String.valueOf(P));
l21a.setText(String.valueOf(Q));
l22a.setText(String.valueOf(R));
}
else if(ae.getActionCommand().equals("master_reset"))
{
l5a.setText("");
l2a.setText("");
l3a.setText("");
l4a.setText("");
}
}
catch (Exception ex)
{
l5a.setText(ex.toString());
// l3a.setText(ex.toString());
}
}
}
After I click the Calculate button (button calc) the calculated values do not appear in the respective labels and an exception is shown saying java.lang.NumberFormatException: Empty string. I am not able to figure out the solution. please help.

the line exchange_rate = Double.parseDouble(l4a.getText()); gives you this exception, because there is no value in l4a and you are trying to parse it into a double value,
try printing the exception in the catch clause.

It's probably a relatively safe bet to say that it is happening here at the beginning of your function, though you should provide the actual exception and line number for us.
quantity = Double.parseDouble(l2a.getText());
invoice_value = Double.parseDouble(l3a.getText());
exchange_rate = Double.parseDouble(l4a.getText());
M = Double.parseDouble(l17a.getText());
N = Double.parseDouble(l18a.getText());
O = Double.parseDouble(l19a.getText());
Make sure that each of these fields actually has numeric text in it. I would recommend putting a logging line or an alert line to state their values before this is executed. Better yet, you can catch the first line in a debugger and look at the the values of all of the items you're calling getText() on. I bet one has an empty string.

Unable to getText the value of string

I'm preparing a simple system as my assignment, And I'm facing a problem where I dont know how to getText the value of String. I know how to do it with integer, but not with string.
I use Integer.parseInt(t2.getText()); in my code if i want to get an integer value
I have added my code into this.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class tollRate extends JFrame implements ActionListener {
JLabel L1 = new JLabel("Please insert your origin (in capital letter)");
JTextField t1 = new JTextField(20);
JLabel L2 = new JLabel("Please insert your destination (in capital letter)");
JTextField t2 = new JTextField(20);
JLabel L3 = new JLabel("Your vehicle class");
JTextField t3 = new JTextField(1);
JButton b1 = new JButton("Calculate");
JButton b2 = new JButton("Exit");
JLabel L4 = new JLabel("Class 0 : Motorcycles, bicycles, or vehicles with "
+ "2 or less wheels" + "\nClass 1 : Vehicles wit 2 axles and 3 "
+ "or 4 wheels excluding taxis" + "\nClass 2 : Vehicles with 2 "
+ "axles and 5 or 6 wheels excluding busses" + "\n Class 3 : "
+ "Vehicles with 3 or more axles" + "\nClass 4 : Taxis"
+ "\nClass 5 : Buses");
JPanel p1 = new JPanel();
JPanel p2 = new JPanel();
JPanel p3 = new JPanel();
JPanel p4 = new JPanel();
JPanel p5 = new JPanel();
String i, j, k;
tollRate() {
JFrame a = new JFrame();
setTitle("Highway Toll Rates System");
setSize(600, 400);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new GridLayout(5, 2));
p1.setLayout(new GridLayout(1, 2));
p1.add(L1);
p1.add(t1);
p2.setLayout(new GridLayout(1, 2));
p2.add(L2);
p2.add(t2);
p3.setLayout(new GridLayout(1, 2));
p3.add(L3);
p3.add(t3);
p4.setLayout(new FlowLayout());
p4.add(b1);
p4.add(b2);
p5.setLayout(new FlowLayout());
p5.add(L4);
add(p1);
add(p2);
add(p3);
add(p4);
add(p5);
b1.addActionListener(this);
b2.addActionListener(this);
}
public void actionPerformed(ActionEvent a) {
Object source = a.getSource();
if (source == b2) {
this.dispose();
} else if (source == b1) {
i = Integer.parseInt(t1.getText());
j = Integer.parseInt(t2.getText());
k = Integer.parseInt(t3.getText());
}
}
public static void main(String[] args) {
tollRate a = new tollRate();
}
}

First of all String i, j, k;
i = Integer.parseInt(t1.getText());
j = Integer.parseInt(t2.getText());
k = Integer.parseInt(t3.getText());
This is wrong. You are assigning String for int. Correct them first. and if you want int values it is better to use
int i, j, k; and use trim() to avoid additional spaces.
i = Integer.parseInt(t1.getText().trim());
j = Integer.parseInt(t2.getText().trim());
k = Integer.parseInt(t3.getText().trim());
In your case use as follows
i = t1.getText();
j = t2.getText();
k = t3.getText();

to assign a string to a string all you need to do is
i = t1.getText();
j = t2.getText();
k = t3.getText();
as you have created them as strings already

Components added outside constructor wont appear

I have one tab that needs to update using one of two methods in it's class while the program is running, for that reason I'm adding components inside the methods, and I cannot get any of them to display. As far as I can tell it's because they are outside the constructor, I used to declare them all inside the methods but moved it to try and fix the problem. Any help would be greatly appreciated.
I apologise it's a bit messy, I've been trying to fix the problem, a bit blindly.
Also the code compiles fine, and println outputs in code display as expected.
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package assgui;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.io.*;
/**
*
* #author Hugh
*/
public class ResultPanel extends JPanel {
static String[][] activityString = new String[31][2];
static String[][] foodString = new String[36][2];
String weighstr, foodstr, servstr, kjstr, actstr, hourstr, minstr, metstr;
JLabel uw = new JLabel ("User Weight: ");
JLabel weigh = new JLabel (weighstr);
JLabel kg = new JLabel(" kg");
JLabel sel1 = new JLabel("Food: ");
JLabel sel2 = new JLabel(foodstr);
JLabel sel3 = new JLabel(" - kj ");
JLabel sel4 = new JLabel(kjstr);
JLabel sel5 = new JLabel(" , Servings: ");
JLabel sel6 = new JLabel(servstr);
JLabel sel7 = new JLabel("Activity for comparison: ");
JLabel sel8 = new JLabel(actstr);
JLabel sel9 = new JLabel(" Time required to balance: ");
JLabel sel10 = new JLabel(hourstr);
JLabel sel11 = new JLabel(" hours");
JLabel sel12 = new JLabel(minstr);
JLabel sel13 = new JLabel(" minutes");
JLabel smlspace = new JLabel(" ");
JLabel medspace = new JLabel(" ");
JLabel lrgspace = new JLabel(" ");
JLabel auw = new JLabel("User Weight: ");
JLabel aweigh = new JLabel(weighstr);
JLabel akg = new JLabel(" kg");
JLabel asel1 = new JLabel("Activity: ");
JLabel asel2 = new JLabel(actstr);
JLabel asel3 = new JLabel(" - MET ");
JLabel asel4 = new JLabel(metstr);
JLabel asel5 = new JLabel(" , Duration: ");
JLabel asel6 = new JLabel(hourstr);
JLabel asel7 = new JLabel(" hour ");
JLabel asel8 = new JLabel(minstr);
JLabel asel9 = new JLabel(" minutes ");
JLabel asel10 = new JLabel("Food for comparison: ");
JLabel asel11 = new JLabel(foodstr);
JLabel asel12 = new JLabel(" Servings to balance: ");
JLabel asel13 = new JLabel(servstr);
JLabel asmlspace = new JLabel(" ");
JLabel amedspace = new JLabel(" ");
JLabel alrgspace = new JLabel(" ");
Public ResultPanel() {
setBackground(Color.GREEN);
setPreferredSize(new Dimension(650, 600));
{
public void activityPaint (String[][] actstring, String[][] foodstring, double weight, int activity, int hour, int min, int food, double servings) {
System.out.println("act1");
weighstr = Double.toString(weight);
actstr = activityString[activity][0];
hourstr = Integer.toString(hour);
minstr = Integer.toString(min);
metstr = activityString[activity][1];
foodstr = foodString[food][0];
servstr = Double.toString(servings);
add(lrgspace);
add(uw);
add(weigh);
add(kg);
add(medspace);
add(sel1);
add(sel2);
add(sel3);
add(sel4);
add(sel5);
add(sel6);
add(sel7);
add(sel8);
add(sel9);
add(sel10);
add(sel11);
add(sel12);
add(sel13);
}
public void foodPaint(String[][] foodstring, String[][] actstring, double weight, int food, int servings, int activity, int hour, int min) {
System.out.println("food1");
weighstr = Double.toString(weight);
foodstr = foodString[food][0];
servstr = Integer.toString(servings);
kjstr = foodString[food][1];
actstr = activityString[activity][0];
hourstr = Integer.toString(hour);
minstr = Integer.toString(min);
add(lrgspace);
add(uw);
add(weigh);
add(kg);
add(medspace);
add(sel1);
add(sel2);
add(sel3);
add(sel4);
add(sel5);
add(sel6);
add(sel7);
add(sel8);
add(sel9);
add(sel10);
add(sel11);
add(sel12);
add(sel13);
}
}

Does your main method (or whatever method) that creates this JPanel also call the activityPaint(...) and foodPaint(...) methods? If those methods are not called then they will never be added to the panel it seems. If you want everything to be added when you create the JPanel then you must have your constructor call activityPaint() and foodPaint().
If the values of your JLables can't be set until something else occurs (like user input), then you can add the components when the JPanel is created and then later call the setText(...) method. Just be sure if you do that to also set the size since changing the text will effect that. I prefer to use nameofjpanel.setSize(nameofjpanel.getPreferredSize()).
Hope this helps you and I didn't completely miss what you're going for here.

Java radio buttons

I'm having trouble with my radio buttons. I can click on all three at the same time. It should be when you click on one the other one turns off?
I'm using a grid layout. So when I try group.add it doesn't work.
Example:
I have the buttons declared like this
JRadioButton seven = new JRadioButton("7 years at 5.35%", false);
JRadioButton fifteen = new JRadioButton("15 years at 5.5%", false);
JRadioButton thirty = new JRadioButton("30 years at 5.75%", false);
ButtonGroup group = new ButtonGroup();
grid.add(seven);
grid.add(fifteen);
grid.add(thirty);
This is my code:
/*Change Request #6
Write the program in Java (with a graphical user interface)
so that it will allow the user to select which way
they want to calculate a mortgage:
by input of the amount of the mortgage,
the term of the mortgage,
and the interest rate of the mortgage payment
or by input of the amount of a mortgage and
then select from a menu of mortgage loans:
- 7 year at 5.35%
- 15 year at 5.5 %
- 30 year at 5.75%
In either case, display the mortgage payment amount
and then, list the loan balance and interest paid
for each payment over the term of the loan.
Allow the user to loop back and enter a new amount
and make a new selection, or quit.
Insert comments in the program to document the program.
*/
import java.text.NumberFormat;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class WK4 extends JFrame implements ActionListener
{
int loanTerms[] = { 7, 15, 30 };
double annualRates[] = { 5.35, 5.5, 5.75 };
// Labels
JLabel AmountLabel = new JLabel(" Loan Amount $ ");
JLabel PaymentLabel = new JLabel(" Monthly Payment ");
JLabel InterestLabel = new JLabel(" Interest Rate % ");
JLabel TermLabel = new JLabel(" Years of Loan ");
// Text Fields
JTextField mortgageAmount = new JTextField(6);
JTextField Payment = new JTextField(6);
JTextField InterestRate = new JTextField(3);
JTextField Term = new JTextField(3);
// Radio Buttons
ButtonGroup radioGroup = new ButtonGroup();
JRadioButton seven = new JRadioButton("7 years at 5.35%");
JRadioButton fifteen = new JRadioButton("15 years at 5.5%");
JRadioButton thirty = new JRadioButton("30 years at 5.75%");
// Buttons
JButton exitButton = new JButton("Exit");
JButton resetButton = new JButton("Reset");
JButton calculateButton = new JButton("Calculate ");
// Text Area
JTextArea LoanPayments = new JTextArea(20, 50);
JTextArea GraphArea = new JTextArea(20, 50);
JScrollPane scroll = new JScrollPane(LoanPayments);
public WK4(){
super("Mortgage Calculator");
//Window
setSize(700, 400);
setLocation(200, 150);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel pane = new JPanel(new GridLayout(2, 2));
Container grid = getContentPane();
grid.setLayout(new GridLayout(4, 10, 0, 12)); //rows, cols, hgap, vgap
pane.add(grid);
pane.add(scroll);
grid.add(AmountLabel);
grid.add(mortgageAmount);
grid.add(InterestLabel);
grid.add(InterestRate);
grid.add(TermLabel);
grid.add(Term);
grid.add(PaymentLabel);
grid.add(Payment);
grid.add(Box.createHorizontalStrut(15));
ButtonGroup group = new ButtonGroup();
grid.add(seven);
grid.add(fifteen);
grid.add(thirty);
grid.add(calculateButton);
grid.add(resetButton);
grid.add(exitButton);
Payment.setEditable(false);
setContentPane(pane);
setContentPane(pane);
setVisible(true);
// Action Listeners
mortgageAmount.addActionListener(this);
InterestRate.addActionListener(this);
Term.addActionListener(this);
Payment.addActionListener(this);
seven.addActionListener(this);
fifteen.addActionListener(this);
thirty.addActionListener(this);
calculateButton.addActionListener(this);
exitButton.addActionListener(this);
resetButton.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
Object command = e.getSource();
if (command == exitButton) {
System.exit(0);
}
else if (command == seven) {
calcLoan(loanTerms[0], annualRates[0]);
}
else if (command == fifteen) {
calcLoan(loanTerms[1], annualRates[1]);
}
else if (command == thirty) {
calcLoan(loanTerms[2], annualRates[2]);
}
else if (command == calculateButton) {
double years = 0;
double rates = 0;
try {
years = Double.parseDouble(Term.getText());
rates = Double.parseDouble(InterestRate.getText());
}
catch (Exception ex) {
LoanPayments.setText("Invalid Amount");
return;
}
calcLoan(years, rates);
}
else if (command == resetButton) {
mortgageAmount.setText("");
Payment.setText("");
InterestRate.setText("");
Term.setText("");
LoanPayments.setText("");
}
}
private void calcLoan(double years, double rates) {
Term.setText(String.valueOf(years));
InterestRate.setText(String.valueOf(rates));
double amount = 0;
try {
amount = Double.parseDouble(mortgageAmount.getText());
}
catch (Exception ex) {
LoanPayments.setText("Invalid Amount");
return;
}
double interestRate = rates;
double intRate = (interestRate / 100) / 12;
int months = (int) years * 12;
double rate = (intRate / 12);
double payment = amount * intRate
/ (1 - (Math.pow(1 / (1 + intRate), months)));
double remainingPrincipal = amount;
double MonthlyInterest = 0;
double MonthlyAmt = 0;
NumberFormat CurrencyFormatter = NumberFormat.getCurrencyInstance();
Payment.setText(CurrencyFormatter.format(payment));
LoanPayments.setText(" Month\tPrincipal\tInterest\tEnding Balance\n");
int currentMonth = 0;
while (currentMonth < months) {
MonthlyInterest = (remainingPrincipal * intRate);
MonthlyAmt = (payment - MonthlyInterest);
remainingPrincipal = (remainingPrincipal - MonthlyAmt);
LoanPayments.append((++currentMonth) + "\t"
+ CurrencyFormatter.format(MonthlyAmt) + "\t"
+ CurrencyFormatter.format(MonthlyInterest) + "\t"
+ CurrencyFormatter.format(remainingPrincipal) + "\n");
GraphArea.append("" + remainingPrincipal);
}
}
public static void main(String[] args) {
new WK4();
}
}

You're adding the radio buttons to the grid but you also need to add them to the button group that you defined.
Maybe this:
ButtonGroup group = new ButtonGroup();
grid.add(seven);
grid.add(fifteen);
grid.add(thirty);
Should be this: ??? (Copy/paste bug?)
ButtonGroup group = new ButtonGroup();
group.add(seven);
group.add(fifteen);
group.add(thirty);
Or maybe you need to do both. The radio buttons have to belong to a container as well as a button group to be displayed and to behave properly.