import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class PaymentCalculator extends JFrame{
 private JPanel panelTitle,panelInput,panelButtons;
    private JLabel lbltuition, lblmisc, lblscholarship, lblfee;
    private JTextField txttuition, txtmisc;
    private JComboBox cbscholarship;
    private JRadioButton optfull, opttuition,optOther;
    private ButtonGroup btnpayment;
    private JCheckBox chkfees1, chkfees2, chkfees3;
    private JButton btncompute, btnclear;
    private JList listbuy;
    private DefaultListModel listmodel;
    private JFrame myFrame,myFrame2;
    private double fee=0;


    public PaymentCalculator() {
        super("Payment Calculator");
         setLayout(new BorderLayout());
        panelInput = new JPanel();
    add(panelInput, BorderLayout.CENTER);


    panelInput.setLayout(new GridLayout(10,5,5,5));

        lbltuition = new JLabel("Tuition Fee:");
        //lbltuition.setBounds(10, 25, 120, 30);
        panelInput.add(lbltuition);
        txttuition = new JTextField(10);
        txttuition.setText("0.0");
        //txttuition.setBounds(170, 30, 80,60);
        panelInput.add(txttuition);


        lblmisc = new JLabel("Miscellaneous Fee:");
       // lblmisc.setBounds(10, 55, 120, 30);
        panelInput.add(lblmisc);
        txtmisc = new JTextField(10);
        txtmisc.setText("0.0");
        //txtmisc.setBounds(170, 60, 80, 30);
        panelInput.add(txtmisc);



        String[] strScholar = {"", "", "", "OWA"};
        lblscholarship = new JLabel("Scholarship:");
        lblscholarship.setBounds(10, 90, 120, 30);
        panelInput.add(lblscholarship);
         cbscholarship = new JComboBox(strScholar);
         cbscholarship.setBounds(130, 95, 135, 20);
        panelInput.add( cbscholarship);

        optfull = new JRadioButton("Full");

        optfull.setBounds(20, 120, 50, 20);
        panelInput.add(optfull);
        opttuition = new JRadioButton("Tuition Only");

        opttuition.setBounds(70, 120, 100, 20);
        panelInput.add(opttuition);


        btnpayment = new ButtonGroup();
        btnpayment.add(optfull);
        btnpayment.add(opttuition);

         JLabel optOther = new JLabel("Other Fees:");
        optOther.setBounds(50, 140, 100, 20);
        panelInput.add(optOther);

        chkfees1 = new JCheckBox("PE Shirt (500.00)");
        chkfees1.setBounds(125, 140, 120, 20);
        chkfees2 = new JCheckBox("Lab Manual (200.00)");
        chkfees2.setBounds(125, 160, 150, 20);
        chkfees3 = new JCheckBox("Lab Gown (100.00)");
        chkfees3.setBounds(125, 180, 150, 20);
        chkfees1.setMnemonic(500);
        chkfees2.setMnemonic(200);
        chkfees3.setMnemonic(100);
        panelInput.add(chkfees1);
        panelInput.add(chkfees2);
        panelInput.add(chkfees3);

         panelButtons = new JPanel();
        panelButtons.setLayout(new GridLayout(4,2));
        btncompute = new JButton("Compute");
        btncompute.setBounds(25, 220, 100, 20);
        panelInput.add(btncompute);
        btnclear = new JButton("Clear");
        btnclear.setBounds(155, 220, 100, 20);
        panelInput.add(btnclear);

        ActionListener listener = new ButtonListener();
        btncompute.addActionListener(listener);
        btnclear.addActionListener(listener);

        ItemListener item = new ItemHandler();
        chkfees1.addItemListener(item);
        chkfees2.addItemListener(item);
        chkfees3.addItemListener(item);
        listmodel = new DefaultListModel();
        listbuy = new JList(listmodel);




    }

    public class ButtonListener implements ActionListener {

        public void actionPerformed(ActionEvent evt) {
            JButton btnchoose = (JButton) evt.getSource();
            double tuition = Integer.parseInt(txttuition.getText());

            double misc = Integer.parseInt(txtmisc.getText());

            if (btnchoose == btncompute) {
                int answer = JOptionPane.showConfirmDialog(null, "Confirm Payment?", "Payment", JOptionPane.YES_NO_OPTION);
                switch (answer) {

                    case JOptionPane.YES_OPTION:

                        if ((chkfees1.isSelected() == true) && (chkfees2.isSelected() == true) && (chkfees3.isSelected() == true)) {
                            fee = tuition + misc + chkfees1.getMnemonic() + chkfees2.getMnemonic() + chkfees3.getMnemonic();
                        } else if ((chkfees2.isSelected() == true) && (chkfees3.isSelected() == true)) {
                            fee = tuition + misc + chkfees2.getMnemonic() + chkfees3.getMnemonic();
                        } else if ((chkfees1.isSelected() == true) && (chkfees2.isSelected() == true)) {
                            fee = tuition + misc + chkfees1.getMnemonic() + chkfees2.getMnemonic();
                        } else if ((chkfees1.isSelected() == true) && (chkfees3.isSelected() == true)) {
                            fee = tuition+ misc + chkfees1.getMnemonic() + chkfees3.getMnemonic();
                        } else if ((chkfees1.isSelected() == true)) {
                            fee = tuition + misc + chkfees1.getMnemonic();
                        } else if ((chkfees2.isSelected() == true)) {
                            fee = tuition  + misc + chkfees2.getMnemonic();
                        } else if ((chkfees3.isSelected() == true)) {
                            fee = (tuition ) + misc + chkfees3.getMnemonic();
                        } else {
                            fee = tuition + misc;
                        }

                       new Payment();
                        break;
                       case JOptionPane.NO_OPTION:

                        break;  }
            } 
            else if (btnchoose == btnclear) {
                txttuition.setText("0");
                txtmisc.setText("0");
                chkfees1.setSelected(false);
                chkfees2.setSelected(false);
                chkfees3.setSelected(false);
                cbscholarship.setSelectedIndex(0);
                btnpayment.clearSelection();
                lblfee.setText("");
                return;
            }
        }
    }

 private class ItemHandler implements ItemListener {

        public void itemStateChanged(ItemEvent e) {
            Object select = e.getItemSelectable();
            if (select == chkfees1) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    listmodel.addElement(chkfees1.getText());

                } else {
                    listmodel.removeElement(chkfees1.getText());
                }
            } if (select == chkfees2) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    listmodel.addElement(chkfees2.getText());

                } else {
                    listmodel.removeElement(chkfees2.getText());
                }
            } if (select ==chkfees3) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    listmodel.addElement(chkfees3.getText());

                } else {
                    listmodel.removeElement(chkfees3.getText());
                }
            }

        }
    }


public class Payment extends JFrame{
    public Payment(){
                       super("Total Payment");
                        setLayout(new FlowLayout());
                       getContentPane().setBackground(Color.white);
                        lblfee = new JLabel("Overall Fee: "+fee);
                        lblfee.setBounds(10, 10, 120, 50);
                        add(lblfee);
                       setBounds(120,220,200,100);
                        setSize(230, 100);
                        setVisible(true);

    }
    }

    public void run() {
        setSize(300, 300);

        setLocationRelativeTo(null);

        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {

        PaymentCalculator tuition = new PaymentCalculator();
        tuition.run();


    }
}

by writing it in a JInternalFrame instead in a JFrame?

a few remarks on your if statements:

if ((chkfees1.isSelected() == true) && (chkfees2.isSelected() == true) && (chkfees3.isSelected() == true))

this can be rewritten as:

if ( chkfees1.isSelected() && chkfees2.isSelected() && chkfees3.isSelected())

makes it a lot easier to read.

in your itemhandler:

 if (select == chkfees1) {
// further code
} if (select == chkfees2) {
//further code
} if (select ==chkfees3) {
//further code
}

especially when you have a lot of these, use if else-if, instead of if - if
now you will run all three checks, even if select is chkfees1.

 if (select == chkfees1) {
// further code
}else if (select == chkfees2) {
//further code
}else if (select ==chkfees3) {
//further code
}

like this: if select is chkfees1, the other two if statements won't run, since it's already known they'll never be true.

Ok thanks :).. but how can i put these codes within the internal frame?

import java.awt.*;
import javax.swing.*;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
   import java.awt.event.*;
public class MainFrame extends JFrame{
     private JPanel panelTitle,panelInput,panelButtons;
    private JLabel lbltuition, lblmisc, lblscholarship, lblfee;
    private JTextField txttuition, txtmisc;
    private JComboBox cbscholarship;
    private JRadioButton optfull, opttuition,optOther;
    private ButtonGroup btnpayment;
    private JCheckBox chkfees1, chkfees2, chkfees3;
    private JButton btncompute, btnclear;
    private JList listbuy;
    private DefaultListModel listmodel;
    private JFrame myFrame,myFrame2;
    private double fee=0;

    public MainFrame(){

     JInternalFrame iframe = new JInternalFrame("Payment Calculator", true, true, true, true);  
         panelInput = new JPanel();
    add(panelInput, BorderLayout.CENTER);


    panelInput.setLayout(new GridLayout(10,5,5,5));

        lbltuition = new JLabel("Tuition Fee:");

        panelInput.add(lbltuition);
        txttuition = new JTextField(10);
        txttuition.setText("0.0");

        panelInput.add(txttuition);


        lblmisc = new JLabel("Miscellaneous Fee:");

        panelInput.add(lblmisc);
        txtmisc = new JTextField(10);
        txtmisc.setText("0.0");

        panelInput.add(txtmisc);



        String[] strScholar = {"", "", "", "OWA"};
        lblscholarship = new JLabel("Scholarship:");
        lblscholarship.setBounds(10, 90, 120, 30);
        panelInput.add(lblscholarship);
         cbscholarship = new JComboBox(strScholar);
         cbscholarship.setBounds(130, 95, 135, 20);
        panelInput.add( cbscholarship);

        optfull = new JRadioButton("Full");

        optfull.setBounds(20, 120, 50, 20);
        panelInput.add(optfull);
        opttuition = new JRadioButton("Tuition Only");

        opttuition.setBounds(70, 120, 100, 20);
        panelInput.add(opttuition);


        btnpayment = new ButtonGroup();
        btnpayment.add(optfull);
        btnpayment.add(opttuition);

         JLabel optOther = new JLabel("Other Fees:");
        optOther.setBounds(50, 140, 100, 20);
        panelInput.add(optOther);

        chkfees1 = new JCheckBox("PE Shirt (500.00)");
        chkfees1.setBounds(125, 140, 120, 20);
        chkfees2 = new JCheckBox("Lab Manual (200.00)");
        chkfees2.setBounds(125, 160, 150, 20);
        chkfees3 = new JCheckBox("Lab Gown (100.00)");
        chkfees3.setBounds(125, 180, 150, 20);
        chkfees1.setMnemonic(500);
        chkfees2.setMnemonic(200);
        chkfees3.setMnemonic(100);
        panelInput.add(chkfees1);
        panelInput.add(chkfees2);
        panelInput.add(chkfees3);

         panelButtons = new JPanel();
        panelButtons.setLayout(new GridLayout(4,2));
        btncompute = new JButton("Compute");
        btncompute.setBounds(25, 220, 100, 20);
        panelInput.add(btncompute);
        btnclear = new JButton("Clear");
        btnclear.setBounds(155, 220, 100, 20);
        panelInput.add(btnclear);




        iframe.setSize(300,300);  
        iframe.setLocation(50,50);  
        iframe.setVisible(true); 



        JDesktopPane desktop = new JDesktopPane();  
        desktop.add(iframe);  

        JFrame f = new JFrame();  

        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  

        f.getContentPane().add(desktop);  
        f.setSize(500,500);  
        f.setLocation(200,200);  
        f.setVisible(true);
    }

         public class ButtonListener implements ActionListener {

        public void actionPerformed(ActionEvent evt) {
            JButton btnchoose = (JButton) evt.getSource();
            double tuition = Integer.parseInt(txttuition.getText());

            double misc = Integer.parseInt(txtmisc.getText());

            if (btnchoose == btncompute) {
                int answer = JOptionPane.showConfirmDialog(null, "Confirm Payment?", "Payment", JOptionPane.YES_NO_OPTION);
                switch (answer) {

                    case JOptionPane.YES_OPTION:

                        if ((chkfees1.isSelected() == true) && (chkfees2.isSelected() == true) && (chkfees3.isSelected() == true)) {
                            fee = tuition + misc + chkfees1.getMnemonic() + chkfees2.getMnemonic() + chkfees3.getMnemonic();
                        } else if ((chkfees2.isSelected() == true) && (chkfees3.isSelected() == true)) {
                            fee = tuition + misc + chkfees2.getMnemonic() + chkfees3.getMnemonic();
                        } else if ((chkfees1.isSelected() == true) && (chkfees2.isSelected() == true)) {
                            fee = tuition + misc + chkfees1.getMnemonic() + chkfees2.getMnemonic();
                        } else if ((chkfees1.isSelected() == true) && (chkfees3.isSelected() == true)) {
                            fee = tuition+ misc + chkfees1.getMnemonic() + chkfees3.getMnemonic();
                        } else if ((chkfees1.isSelected() == true)) {
                            fee = tuition + misc + chkfees1.getMnemonic();
                        } else if ((chkfees2.isSelected() == true)) {
                            fee = tuition  + misc + chkfees2.getMnemonic();
                        } else if ((chkfees3.isSelected() == true)) {
                            fee = (tuition ) + misc + chkfees3.getMnemonic();
                        } else {
                            fee = tuition + misc;
                        }

                       new Payment();
                        break;
                       case JOptionPane.NO_OPTION:

                        break;  }
            } 
            else if (btnchoose == btnclear) {
                txttuition.setText("0");
                txtmisc.setText("0");
                chkfees1.setSelected(false);
                chkfees2.setSelected(false);
                chkfees3.setSelected(false);
                cbscholarship.setSelectedIndex(0);
                btnpayment.clearSelection();
                lblfee.setText("");
                return;
            }
        }
    }

 private class ItemHandler implements ItemListener {

        public void itemStateChanged(ItemEvent e) {
            Object select = e.getItemSelectable();
            if (select == chkfees1) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    listmodel.addElement(chkfees1.getText());

                } else {
                    listmodel.removeElement(chkfees1.getText());
                }
            } if (select == chkfees2) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    listmodel.addElement(chkfees2.getText());

                } else {
                    listmodel.removeElement(chkfees2.getText());
                }
            } if (select ==chkfees3) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    listmodel.addElement(chkfees3.getText());

                } else {
                    listmodel.removeElement(chkfees3.getText());
                }
            }

        }
    }

 public class Payment extends JFrame{
    public Payment(){
                       super("Total Payment");
                        setLayout(new FlowLayout());
                       getContentPane().setBackground(Color.white);
                        lblfee = new JLabel("Overall Fee: "+fee);
                        lblfee.setBounds(10, 10, 120, 50);
                        add(lblfee);
                       setBounds(120,220,200,100);
                        setSize(230, 100);
                        setVisible(true);

    }
    }

 public static void main(String[] args)  
    {  
        new MainFrame();  

    }  
}

ok so this is my program with internalframe, i dont know how to put Payment Calculator codes within the internalframe

you have to add the components to the interalFrame. the 'add(Component comp)' method is used for that.

for instance: right before your iframe.setSize(300,300);
add the line
iframe.add(panelInput);

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