Help with JFrame program that calculates average

**ePerKar3** · November 3rd, 2011, 08:59 PM

Hi everyone. I have a program i'm working on for an assignment that is pretty basic but i still can't get it to work, i'm still really new to Java. This program along with a few others are already way overdue so any quick help would be greatly appreciated.

The program is a JFrame program that reads three values from the user and then calculates the average value. It has to be formatted so that the output average contains two decimals and the user can input the decimals using either a comma or a dot and it should work either way. Here is the code i have so far:

package MOM1;
 
import java.text.DecimalFormat;
 
public class Average extends javax.swing.JFrame {
 
    /** Creates new form Average */
    public Average() {
        initComponents();
    }
 
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
 
        jButton1 = new javax.swing.JButton();
        jTextField1 = new javax.swing.JTextField();
        jTextField2 = new javax.swing.JTextField();
        jTextField3 = new javax.swing.JTextField();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jTextFieldAverage = new javax.swing.JTextField();
        jLabel4 = new javax.swing.JLabel();
 
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(new java.awt.Color(153, 255, 255));
 
        jButton1.setText("Räkna ut");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });
 
        jLabel1.setText("Tal 1");
 
        jLabel2.setText("Tal 2");
 
        jLabel3.setText("Tal 3");
 
        jLabel4.setText("Medelvärde:");
 
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(47, 47, 47)
                        .addComponent(jLabel1)
                        .addGap(103, 103, 103)
                        .addComponent(jLabel2)
                        .addGap(93, 93, 93)
                        .addComponent(jLabel3))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(152, 152, 152)
                        .addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, 209, Short.MAX_VALUE))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(130, 130, 130)
                        .addComponent(jTextFieldAverage, javax.swing.GroupLayout.PREFERRED_SIZE, 97, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap())
            .addGroup(layout.createSequentialGroup()
                .addGap(29, 29, 29)
                .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(62, 62, 62)
                .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 48, Short.MAX_VALUE)
                .addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, 65, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(40, 40, 40))
            .addGroup(layout.createSequentialGroup()
                .addGap(109, 109, 109)
                .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 135, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(127, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel1)
                            .addComponent(jLabel2)
                            .addComponent(jLabel3)))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(28, 28, 28)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))))
                .addGap(18, 18, 18)
                .addComponent(jLabel4)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jTextFieldAverage, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
 
        pack();
    }// </editor-fold>                        
 
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    /* Reads input from the three fields, parses them from
     * string to double and saves them in variables of type
     * double.
     */
 
    DecimalFormat df1=new DecimalFormat("##.00");
 
    String talet1 = null;
    String talet2 = null;
    String talet3 = null;
    double tal1;
    double tal2;
    double tal3;
    double medel;
 
    if (jTextField1.getText().contains(","))
    {
        talet1=jTextField1.getText().replace(',', '.');
    }
    else
    {
        talet1=jTextField1.getText();
    }
 
 
    if (jTextField2.getText().contains(","))
    {
        talet2=jTextField2.getText().replace(',', '.');
    }
    else
    {
        talet2=jTextField2.getText();
    }
 
 
    if (jTextField3.getText().contains(","))
    {
        talet3=jTextField3.getText().replace(',', '.');
    }
    else
    {
        talet3=jTextField3.getText();
    }
 
    tal1 = Double.parseDouble(talet1);
    tal2 = Double.parseDouble(talet2);
    tal3 = Double.parseDouble(talet3);
    medel = (tal1 + tal2 + tal3)/3;
    String svar = DecimalFormat.getInstance().format(medel);
    jTextFieldAverage.setText(df1.format(svar));
}                                        
 
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(Average.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Average.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Average.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Average.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
 
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
 
            public void run() {
                new Average().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    private javax.swing.JTextField jTextField3;
    private javax.swing.JTextField jTextFieldAverage;
    // End of variables declaration                   
}

And these are the errors i get whenever i press the calculate button:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1008)
	at java.lang.Double.parseDouble(Double.java:540)
	at MOM1.Average.jButton1ActionPerformed(Average.java:121)
	at MOM1.Average.access$000(Average.java:5)
	at MOM1.Average$1.actionPerformed(Average.java:37)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
	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:6504)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
	at java.awt.Component.processEvent(Component.java:6269)
	at java.awt.Container.processEvent(Container.java:2229)
	at java.awt.Component.dispatchEventImpl(Component.java:4860)
	at java.awt.Container.dispatchEventImpl(Container.java:2287)
	at java.awt.Component.dispatchEvent(Component.java:4686)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
	at java.awt.Container.dispatchEventImpl(Container.java:2273)
	at java.awt.Window.dispatchEventImpl(Window.java:2713)
	at java.awt.Component.dispatchEvent(Component.java:4686)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
	at java.awt.EventQueue.access$000(EventQueue.java:101)
	at java.awt.EventQueue$3.run(EventQueue.java:666)
	at java.awt.EventQueue$3.run(EventQueue.java:664)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.awt.EventQueue$4.run(EventQueue.java:680)
	at java.awt.EventQueue$4.run(EventQueue.java:678)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

What am i doing wrong and how can i fix it?

**macko** · November 3rd, 2011, 09:09 PM

Decimal format code:

double d = 1.234567;
 DecimalFormat df = new DecimalFormat("#.##");
 System.out.print(df.format(d));

Source: http://www.javaprogrammingforums.com...al-places.html

Maybe if your trying to format multiple variables as different formats create multiple format lines?

**Junky** · November 3rd, 2011, 09:57 PM

at MOM1.Average.jButton1ActionPerformed(Average.java: 121)

Something on line 121 is null. Find out what is null. Find out why it is null. Make sure it is not null.

**copeg** · November 4th, 2011, 08:48 AM

Originally Posted by macko

Decimal format code:
....
Maybe if your trying to format multiple variables as different formats create multiple format lines?

What does this have to do with a NullPointerException?

Thread: Help with JFrame program that calculates average

LinkBack

Thread Tools

Display

Help with JFrame program that calculates average

Related threads:

Re: Help with JFrame program that calculates average

Re: Help with JFrame program that calculates average

Re: Help with JFrame program that calculates average

Similar Threads

Moving Average

Basic program which gets cost, adds tax, gets payment then calculates change.

Moving average

Imitating a JFrame extended program with JPanel; help needed...

Average program with array and loop and JOptionPane.

Tags for this Thread