First off, I am a Java Noob coding in latest version of NetBeans. I am trying to create a program the will allow the user to enter two decimal values: time and earnings in a swing GUI.

Basic Flow

  1. The user will enter the values in two different text fields
  2. user will hit enter button and jTextField1 and jTextField2 will be parsed (double) and validation occurs - This is where my errors start. code compiles but generates errors on the button action
  3. if values are in range - they are stored in a two-dimensional array
  4. a Run Report button can be used to do some calculations and output is sent to a jTextArea
  5. Quit button exits the program

How I'm trying to code the program

I created an object> Ledger

/*
* Ledger - 
* simulates a Ledger with a 2-d Array "page" to hold Doubles
* Allows you to add entries and run reports on the data
 */
package com.kenneth.test1;

/**
 *
 * @author Ken
 */
public class Ledger {
    

    // set # of Columns in array - need only 2 -woud break program if changed
    final private int COLUMN_MAX = 2;

    // @MAX_SESSION_TIME sets the maximum amout of work-time for user
    // could be changed without breaking program
    final private int MAX_SESSION_TIME = 240;

    // @ROW_MAX sets max size of array, could be increased without breaking program
    final private int ROW_MAX = 10;

    // @currentRow keeps track of how many items have been added to array
    // also used for item total to calculate averages
    private int currentRow;

    // @ledger initialize array
    private double[][] ledgerPage;

    // stores numerical data entered into the earnings field
    private double sessionEarnings;

    // stores numerical data entered into the time field
    private double sessionTime;

    // string to hold output messages
    private String verify;

    // **Constructor**\\
    public Ledger() {
        double[][] ledgerPage1 = new double[ROW_MAX][COLUMN_MAX];

        // @currentRow keeps track of how many items have been added to array
        // also used for item total to calculate averages
        

        // stores numerical data entered into the time field
        sessionTime = 0.0;

        // stores numerical data entered into the earnings field
        sessionEarnings = 0.0;

        // string to hold output messages
        verify = "  ";
    }

    /**
     * @return the ROW_MAX
     */
    public int getROW_MAX() {
        return ROW_MAX;
    }

    /**
     * @return the COLUMN_MAX
     */
    public int getCOLUMN_MAX() {
        return COLUMN_MAX;
    }

    /**
     * @return the ledger
     */
    public double[][] getLedgerPage() {
        return ledgerPage;
    }

    /**
     * @param ledger the ledger to set
     */
    public void setLedgerPage(double[][] x) {
        this.ledgerPage = x;
    }

    /**
     * @return the currentRow
     */
    public int getCurrentRow() {
        return currentRow;
    }

    /**
     * @param currentRow the currentRow to set
     */
    public void setCurrentRow(int currentRow) {
        this.currentRow = currentRow;
    }

    /**
     * @return the sessionTime
     */
    public double getSessionTime() {
        return sessionTime;
    }

    /**
     * @param sessionTime the sessionTime to set
     */
    public void setSessionTime(double sessionTime) {
        this.sessionTime = sessionTime;
    }

    /**
     * @return the MAX_SESSION_TIME
     */
    public int getMAX_SESSION_TIME() {
        return MAX_SESSION_TIME;
    }

    /**
     * @return the sessionEarnings
     */
    public double getSessionEarnings() {
        return sessionEarnings;
    }

    /**
     * @param sessionEarnings the sessionEarnings to set
     */
    public void setSessionEarnings(double sessionEarnings) {
        this.sessionEarnings = sessionEarnings;
    }

    /**
     * @return the verify
     */
    public String getVerify() {
        return verify;
    }

    /**
     * @param verify the verify to set
     */
    public void setVerify(String verify) {
        this.verify = verify;
    }

    public void recordEntry(double[][] ledgerPage, int index1, int index2, double value1) {
        this.ledgerPage[index1][index2] = value1;
        
    }

    public double readEntry(double[][] ledgerPage, int[][] index) {
        return sessionTime;
    }
}

I created the Gui via NetBeans visual editor and dragged my Ledger.java object on top of it to link them as stated on Oracle's website.

/*
 * Ken
 * TutorTracker.java
 * program that take time and earnings data and print reports
 * Created on Sep 28, 2011, 1:27:19 PM
 */

package com.kenneth.test1;

public class TutorTrackerMain extends javax.swing.JFrame {
    
 
    /** Creates new form TutorTrackerMain */
    public TutorTrackerMain() {

        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() {

        ledger1 = new weigand.kenneth.task1.Ledger();
        ledger2 = new weigand.kenneth.task1.Ledger();
        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jTextField1 = new javax.swing.JTextField();
        jTextField2 = new javax.swing.JTextField();
        jButton1 = new javax.swing.JButton();
        jPanel2 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();
        jButton2 = new javax.swing.JButton();
        jButton3 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("TutorTracker");

        jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder(null, "Add Entry", javax.swing.border.TitledBorder.DEFAULT_JUSTIFICATION, javax.swing.border.TitledBorder.DEFAULT_POSITION, new java.awt.Font("Tahoma", 1, 10))); // NOI18N

        jLabel1.setText("Time:");

        jLabel2.setText("Earnings:");

        jButton1.setText("Enter");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel2, javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jLabel1, javax.swing.GroupLayout.Alignment.TRAILING))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jTextField1, javax.swing.GroupLayout.DEFAULT_SIZE, 274, Short.MAX_VALUE)
                    .addComponent(jTextField2, javax.swing.GroupLayout.DEFAULT_SIZE, 274, Short.MAX_VALUE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jButton1))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jButton1)))
        );

        jPanel2.setBorder(javax.swing.BorderFactory.createTitledBorder(null, "Reports", javax.swing.border.TitledBorder.DEFAULT_JUSTIFICATION, javax.swing.border.TitledBorder.DEFAULT_POSITION, new java.awt.Font("Tahoma", 1, 10))); // NOI18N

        jTextArea1.setColumns(20);
        jTextArea1.setRows(5);
        jScrollPane1.setViewportView(jTextArea1);

        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 368, Short.MAX_VALUE)
                .addContainerGap())
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 174, Short.MAX_VALUE)
                .addContainerGap())
        );

        jButton2.setText("Run Report");

        jButton3.setText("Quit");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(214, Short.MAX_VALUE)
                .addComponent(jButton2)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jButton3)
                .addGap(6, 6, 6))
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(jPanel2, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );

        layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.awt.Component[] {jButton2, jButton3});

        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton3)
                    .addComponent(jButton2)))
        );

        pack();
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       // try-catch to throw exception on non-number data
        try{
            // parse data to store in array
            ledger1.setSessionTime(Double.parseDouble(jTextField1.getText()));
            ledger1.setSessionEarnings(Double.parseDouble(jTextField2.getText()));
            //while there is room in the array - accept input
            if(ledger1.getCurrentRow() < ledger1.getLedgerPage().length){
                // validate data MAX_SESSION_TIME
                if ((ledger1.getSessionTime() > 0 & ledger1.getSessionTime() <= ledger1.getMAX_SESSION_TIME()) & (ledger1.getSessionEarnings() > 0)){
                    // if values are valid, then add to them to the array
                    ledger1.recordEntry(ledger1.getLedgerPage(), ledger1.getCurrentRow(), 0, ledger1.getSessionTime());
                    ledger1.recordEntry(ledger1.getLedgerPage(), ledger1.getCurrentRow(), 1, ledger1.getSessionEarnings());
                    //incr row
                    ledger1.setCurrentRow((ledger1.getCurrentRow()) + 1);
                    
                    ledger1.setVerify(String.format(" Time: %1.0f Eanings: $%1.2f stored.\n",ledger1.getSessionTime(), ledger1.getSessionEarnings()));
                }
                else{
                     //else display message to user to correct data
                     ledger1.setVerify("Please enter positve decimal numbers."
                                + "\nSession Time in minutes must be between 1-240 \n ");
                }
            } 
            else{
                //else display message to user to correct data
                     ledger1.setVerify("Array is full"
                                + "\nRun a report or quit.\n ");
            }
           // send varifcation message to user
           jTextArea1.append(ledger1.getVerify());
        }
        catch (NumberFormatException e){
            jTextArea1.append("***Invalid Entry***\nPlease enter positve decimal numbers."
                                + "\nSession Time in minutes must be between 1-240 \n ");
        }
    }                                        

    /**
     * @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(TutorTrackerMain.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(TutorTrackerMain.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(TutorTrackerMain.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(TutorTrackerMain.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 TutorTrackerMain().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    private weigand.kenneth.task1.Ledger ledger1;
    private weigand.kenneth.task1.Ledger ledger2;
    // End of variables declaration                   
}

The red portion is my algorithm. The code compiles, but errors out when the Enter button is pushed. I have commented out the nested loops to see if it was my validation loop only but the errors are coming up on all loops.

That makes me suspect that I am not passing values correctly.
The GUI has created a new Ledger object, I am able to pull up all Ledger methods in my Gui Object.
I can't see the 2-d Array from the object though.

I hope that there is something simple that I'm missing and would be very thankful if some kind soul could give me direction.

Thanks!

The code compiles, but errors out when the Enter button is pushed

Please copy and paste here the full text of the error message. That will tell us what is wrong.

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at weigand.kenneth.task1.TutorTrackerMain.jButton1ActionPerformed(TutorTrackerMain.java:155)
	at weigand.kenneth.task1.TutorTrackerMain.access$000(TutorTrackerMain.java:15)
	at weigand.kenneth.task1.TutorTrackerMain$1.actionPerformed(TutorTrackerMain.java:59)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
	at java.awt.Component.processMouseEvent(Component.java:6288)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
	at java.awt.Component.processEvent(Component.java:6053)
	at java.awt.Container.processEvent(Container.java:2041)
	at java.awt.Component.dispatchEventImpl(Component.java:4651)
	at java.awt.Container.dispatchEventImpl(Container.java:2099)
	at java.awt.Component.dispatchEvent(Component.java:4481)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
	at java.awt.Container.dispatchEventImpl(Container.java:2085)
	at java.awt.Window.dispatchEventImpl(Window.java:2478)
	at java.awt.Component.dispatchEvent(Component.java:4481)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:643)
	at java.awt.EventQueue.access$000(EventQueue.java:84)
	at java.awt.EventQueue$1.run(EventQueue.java:602)
	at java.awt.EventQueue$1.run(EventQueue.java:600)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
	at java.awt.EventQueue$2.run(EventQueue.java:616)
	at java.awt.EventQueue$2.run(EventQueue.java:614)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:613)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

a NullPointerException means that the value you are trying to use does not exist.
check your variables, where they are used and where you give them a value.
that might help you find the problem

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at weigand.kenneth.task1.TutorTrackerMain.jButton1ActionPerformed(TutorTrackerMain.java:155)
	at weigand.kenneth.task1.TutorTrackerMain.access$000(TutorTrackerMain.java:15)
	at weigand.kenneth.task1.TutorTrackerMain$1.actionPerformed(TutorTrackerMain.java:59)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
	at java.awt.Component.processMouseEvent(Component.java:6288)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
	at java.awt.Component.processEvent(Component.java:6053)
	at java.awt.Container.processEvent(Container.java:2041)
	at java.awt.Component.dispatchEventImpl(Component.java:4651)
	at java.awt.Container.dispatchEventImpl(Container.java:2099)
	at java.awt.Component.dispatchEvent(Component.java:4481)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
	at java.awt.Container.dispatchEventImpl(Container.java:2085)
	at java.awt.Window.dispatchEventImpl(Window.java:2478)
	at java.awt.Component.dispatchEvent(Component.java:4481)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:643)
	at java.awt.EventQueue.access$000(EventQueue.java:84)
	at java.awt.EventQueue$1.run(EventQueue.java:602)
	at java.awt.EventQueue$1.run(EventQueue.java:600)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
	at java.awt.EventQueue$2.run(EventQueue.java:616)
	at java.awt.EventQueue$2.run(EventQueue.java:614)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:613)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

well? it even tells you what line of your code in what class to check for a variable with a null value. found it?

xception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at weigand.kenneth.task1.TutorTrackerMain.jButton1ActionPerformed(TutorTrackerMain.java:155)

Look at line 155 in your program and see what variable could have a null value.
Then look back through your code to see why that variable does not have a valid value.
If you can not see which variable is null, add a println call immediately before line 155 and print out the values of all the variables used on line 155.

thank you! I will check it out. Does my Ledger Object look okay? geter / setter for my 2-d array?

Got it! Thank you! Makes you feel stupid when the answer is staring you in the face.
Lesson for me today, Pay attention to the error output!!

Thanks again!

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