Calculating values from a jtable column

**victaino** · 05-20-2012, 12:02 PM

Hi everyone,

am trying to sum up the values from a jtable column and display the sum on a jtextfield. I am using defaultTableModel and implements TableModelListener to detect changes on the table. Still the textfield doesnt display the summed up value. this is my code:

Java Code:

 public void tableChanged(TableModelEvent e){
        if (e.getType() == TableModelEvent.INSERT){
          
            int row = jTable1.getRowCount();
            
            for (int i = 0; i <= row; i++){
                Int total += (Integer)jTable1.getValueAt(i,4);
            }
            
            String totalResult = new Integer (total).toString();
        }

This is the code that displays the value on textfield:

Java Code:

private void txtTotalActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        
        txtTotal.setText(totalResult);
    }

i need help pls

**Fubarable** · 05-20-2012, 01:09 PM

That code won't compile ("Int total").

Please show us the real code as this is vitally important for us to see if we're going to have a chance of helping you.
We need to see for example if you really do re-declare total inside of the for loop.

**victaino** · 05-20-2012, 01:21 PM

I actually didnt declare the "int total" in the for loop...sorry about that..error on my part when i was pasting the code here. this is the actual code:

Java Code:

public void tableChanged(TableModelEvent e){
       if (e.getType() == TableModelEvent.INSERT){
          
           int row = jTable1.getRowCount();
           int total=0;
            
           for (int i = 0; i <= row; i++){
               total += (Integer)jTable1.getValueAt(i,4);
           }
            
           String totalResult = new Integer (total).toString();
       }

**Fubarable** · 05-20-2012, 01:34 PM

Thanks for the correction.

Now have you placed System.out.println(...) statements in this block of code? Does it ever get called when you expect that it should be called? If so, are you printing out the values that you are extracting from the table from within the for loop to see if they match with your expectations?

**victaino** · 05-20-2012, 01:56 PM

Originally Posted by Fubarable

Thanks for the correction.

Now have you placed System.out.println(...) statements in this block of code? Does it ever get called when you expect that it should be called? If so, are you printing out the values that you are extracting from the table from within the for loop to see if they match with your expectations?

I haven't done that. Will do that now. Cheers

**victaino** · 05-20-2012, 05:15 PM

Originally Posted by Fubarable

Thanks for the correction.

Now have you placed System.out.println(...) statements in this block of code? Does it ever get called when you expect that it should be called? If so, are you printing out the values that you are extracting from the table from within the for loop to see if they match with your expectations?

used System.out.printf() and it printed out what I'm expecting on the console but still doesnt display it on textfield.

this is the code i used to cast the Int value to String so i can use the use the set method of the textfield:

Java Code:

totalResult = new Integer (total).toString();

**DarrylBurke** · 05-20-2012, 05:27 PM

In the tableChanged(...) code you posted, the variable totalResult goes out of scope on the very next line, so can't possibly be used elsewhere in the program.

To get better help sooner, post a SSCCE (Short, Self Contained, Correct (Compilable), Example) that demonstrates the problem. Not hundreds of lines of code; just enough to illustrate the scenario.

db

**victaino** · 05-21-2012, 03:41 AM

Java Code:

public void tableChanged(TableModelEvent e){
       if (e.getType() == TableModelEvent.INSERT){
           
           int row = jTable1.getRowCount();
           int total=0;
             
           for (int i = 0; i <= row; i++){
               total += (Integer)jTable1.getValueAt(i,4);
           }
             
           totalResult = new Integer (total).toString(); // totalResult is declared as a String instance variable
       }

**victaino** · 05-21-2012, 04:44 AM

i tested my code with a little modification using a button and it worked. but i can't get it to work on tableChanged method. i have added tablemodellistener to the table in question. what am i not doing here.

sample of my working code on jbutton actionPreformed:

Java Code:

 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        int row = jTable1.getRowCount();
            
            for (int i = 0; i < row; i++){
                total += Integer.parseInt(jTable1.getValueAt(i,4).toString());
            }
            
            totalResult = Integer.toString(total);
            txtTotal.setText(totalResult);
        
    }

**Fubarable** · 05-21-2012, 05:01 AM

Originally Posted by victaino

i tested my code with a little modification using a button and it worked. but i can't get it to work on tableChanged method. i have added tablemodellistener to the table in question. what am i not doing here.

You're not creating and posting an SSCCE.

Bugs like these can be subtle, and there's a good chance that the code you're posting has nothing to do with your error, which will just lead to frustration for you and us. Do yourself a favor, read the SSCCE link, then pare down your code to its barest essentials to reproduce the error, and post it here.

**victaino** · 05-21-2012, 05:15 AM

Java Code:

jTable1.getModel().addTableModelListener(this);

public void tableChanged(TableModelEvent e){
        if (e.getType() == TableModelEvent.INSERT){
            int row = jTable1.getRowCount();
            
            for (int i = 0; i < row; i++){
                total += Integer.parseInt(jTable1.getValueAt(i,4).toString()); // int total declared as instance variable
            }
            
            totalResult = Integer.toString(total); // String totalResult declared as instance variable
            System.out.println(totalResult);
            txtTotal.setText(totalResult);
        
        }
        
    }

error

Java Code:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at jomas.Sales.tableChanged(Sales.java:675)
	at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:280)
	at javax.swing.table.AbstractTableModel.fireTableRowsInserted(AbstractTableModel.java:215)
	at javax.swing.table.DefaultTableModel.insertRow(DefaultTableModel.java:359)
	at javax.swing.table.DefaultTableModel.addRow(DefaultTableModel.java:333)
	at javax.swing.table.DefaultTableModel.addRow(DefaultTableModel.java:344)
	at jomas.Sales.jTable1KeyPressed(Sales.java:483)
	at jomas.Sales.access$300(Sales.java:29)
	at jomas.Sales$4.keyPressed(Sales.java:237)
	at java.awt.Component.processKeyEvent(Component.java:6333)
	at javax.swing.JComponent.processKeyEvent(JComponent.java:2801)
	at java.awt.Component.processEvent(Component.java:6152)
	at java.awt.Container.processEvent(Container.java:2083)
	at java.awt.Component.dispatchEventImpl(Component.java:4737)
	at java.awt.Container.dispatchEventImpl(Container.java:2141)
	at java.awt.Component.dispatchEvent(Component.java:4565)
	at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1836)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:712)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:990)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:855)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:676)
	at java.awt.Component.dispatchEventImpl(Component.java:4609)
	at java.awt.Container.dispatchEventImpl(Container.java:2141)
	at java.awt.Window.dispatchEventImpl(Window.java:2482)
	at java.awt.Component.dispatchEvent(Component.java:4565)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:684)
	at java.awt.EventQueue.access$000(EventQueue.java:85)
	at java.awt.EventQueue$1.run(EventQueue.java:643)
	at java.awt.EventQueue$1.run(EventQueue.java:641)
	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:657)
	at java.awt.EventQueue$2.run(EventQueue.java:655)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:654)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

**Junky** · 05-21-2012, 05:17 AM

Something on line 675 is null. Find out what and why.

**DarrylBurke** · 05-21-2012, 05:59 AM

Originally Posted by DarrylBurke

To get better help sooner, post a SSCCE (Short, Self Contained, Correct (Compilable), Example) that demonstrates the problem. Not hundreds of lines of code; just enough to illustrate the scenario.

Originally Posted by Fubarable

You're not creating and posting an SSCCE.

You don't really want help, do you?

db

**victaino** · 05-21-2012, 09:40 PM

don't understand what you mean. i have pasted my code already

**Fubarable** · 05-21-2012, 10:21 PM

Originally Posted by victaino

don't understand what you mean. i have pasted my code already

Please re-read my comment in post #10. Please read the SSCCE link. You seem to have ignored both. If anything is confusing about either, please ask for clarification.

**victaino** · 05-21-2012, 11:23 PM

Java Code:


import java.awt.event.KeyEvent;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import javax.swing.table.DefaultTableModel;
import java.awt.print.*;
import java.awt.*;
import javax.swing.JOptionPane;
import javax.swing.event.TableModelListener;
import javax.swing.event.TableModelEvent;

/**
 *
 * @author Vize
 */
public class Sales extends javax.swing.JInternalFrame implements Printable, TableModelListener{
    
     
   int total = 0;
   String totalResult = null;
   
   // keep track of updated data
   private boolean Update = false;
   int total = 0;
   String totalResult = null;

    /** Creates new form Sales */
    public Sales() {
        initComponents();
    }
 @Override
    public void tableChanged (TableModelEvent e){
        if (e.getType()== TableModelEvent.UPDATE){
          int row = jTable1.getRowCount();
            
            for (int i = 0; i < row; i++){
                total += Integer.parseInt(jTable1.getValueAt(i, 4).toString());// this is where the stack trace keep pointing to
            }
            
            totalResult = Integer.toString(total);
            txtTotal.setText(totalResult);  
        }
    }

error

Java Code:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at jomas.Sales.tableChanged(Sales.java:675)
    at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:280)
    at javax.swing.table.AbstractTableModel.fireTableRowsInserted(AbstractTableModel.java:215)
    at javax.swing.table.DefaultTableModel.insertRow(DefaultTableModel.java:359)
    at javax.swing.table.DefaultTableModel.addRow(DefaultTableModel.java:333)
    at javax.swing.table.DefaultTableModel.addRow(DefaultTableModel.java:344)
    at jomas.Sales.jTable1KeyPressed(Sales.java:483)
    at jomas.Sales.access$300(Sales.java:29)
    at jomas.Sales$4.keyPressed(Sales.java:237)

**Fubarable** · 05-21-2012, 11:26 PM

The code posted above does not comply with the SSCCE specification. Yes it is short, but I cannot compile this code, nor can I run it, test it, reproduce your error.

And so, I still cannot help you. *Again*, if anything about the SSCCE specification or our recommendations confuse, please ask. Otherwise we're going to continue to have a very frustrating conversation.

**victaino** · 05-22-2012, 01:42 PM

hope this meets up with SSCCE spec

Java Code:


import java.awt.EventQueue;

import javax.swing.JInternalFrame;
import java.awt.event.KeyEvent;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import javax.swing.table.DefaultTableModel;
import java.awt.print.*;
import java.awt.*;
import javax.swing.JOptionPane;
import javax.swing.event.TableModelListener;
import javax.swing.event.TableModelEvent;


public class Sale extends JInternalFrame implements TableModelListener {
	
	// declare variables   
		 int total = 0;
		String totalResult = null;
		private javax.swing.JTable jTable1;
		 private javax.swing.JTextField txtTotal;
		private javax.swing.JTextField txtPaid;
		private javax.swing.JTextField txtBalance;
		private javax.swing.JButton jButton1;
	    private javax.swing.JPanel jPanel3;
	    private javax.swing.JScrollPane jScrollPane1;
	    private javax.swing.JPanel jPanel4;
	    private javax.swing.JDesktopPane jdesktop;

	    public Sale(){
	    	
	    	// Initialize object
	        jPanel3 = new javax.swing.JPanel();
	        jScrollPane1 = new javax.swing.JScrollPane();
	        jPanel4 = new javax.swing.JPanel();
	        jButton1 = new javax.swing.JButton();
	        jdesktop = new javax.swing.JDesktopPane();




	    	// set layout and create table
	    	jPanel3.setBorder(new javax.swing.border.SoftBevelBorder(javax.swing.border.BevelBorder.RAISED));

	    	        jTable1.setModel(new javax.swing.table.DefaultTableModel(
	    	            new Object [][] {
	    	                {null, null, null, null, null}
	    	            },
	    	            new String [] {
	    	                "Item", "Quantity", "Unit Price", "Discount", "Subtotal"
	    	            }
	    	        ));
	    	        jTable1.setShowGrid(false);
	    	        jTable1.putClientProperty("terminateEditOnFocusLost", true);
	    	        jTable1.addKeyListener(new java.awt.event.KeyAdapter() {
	    	            public void keyPressed(java.awt.event.KeyEvent evt) {
	    	                keyPressed(evt);
	    	            }
	    	        });
	    	        jScrollPane1.setViewportView(jTable1);

	    	        org.jdesktop.layout.GroupLayout jPanel3Layout = new org.jdesktop.layout.GroupLayout(jPanel3);
	    	        jPanel3.setLayout(jPanel3Layout);
	    	        jPanel3Layout.setHorizontalGroup(
	    	            jPanel3Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
	    	            .add(org.jdesktop.layout.GroupLayout.TRAILING, jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 951, Short.MAX_VALUE)
	    	        );
	    	        jPanel3Layout.setVerticalGroup(
	    	            jPanel3Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
	    	            .add(jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 169, Short.MAX_VALUE)
	    	        );

	    	//set layout and create textfields

	    	org.jdesktop.layout.GroupLayout jPanel4Layout = new org.jdesktop.layout.GroupLayout(jPanel4);
	    	        jPanel4.setLayout(jPanel4Layout);
	    	        jPanel4Layout.setHorizontalGroup(
	    	                        .add(jPanel4Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
	    	                            .add(txtPaid)
	    	                            .add(txtTotal)
	    	                            .add(txtBalance)))
	    	                    .add(org.jdesktop.layout.GroupLayout.TRAILING, jPanel4Layout.createSequentialGroup()
	    	                        .add(0, 0, Short.MAX_VALUE)
	    	                        .add(jButton1))
	    	                .addContainerGap();
	    }
	    	// override tablechanged method

	    	@Override
	    	    public void tableChanged (TableModelEvent e){
	    	        if (e.getType()== TableModelEvent.UPDATE){
	    	          int row = jTable1.getRowCount();
	    	            
	    	            for (int i = 0; i < row; i++){
	    	                total += Integer.parseInt(jTable1.getValueAt(i, 4).toString());
	    	            }
	    	            
	    	            totalResult = Integer.toString(total);
	    	            txtTotal.setText(totalResult);  
	    	        }
	    	    }

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					Sale frame = new Sale();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	

}

**Fubarable** · 05-22-2012, 03:24 PM

My compiler is not tolerating your GroupLayout objects. Is this from a NetBeans' project?

**Fubarable** · 05-22-2012, 03:42 PM

Also, since this is a JInternalFrame, doesn't it need to be inside of a JDesktopPane to be displayed?
Usually when I'm creating an SSCCE like this, I use the simplest layout possible, often a JPanel's default FlowLayout, and then put the main JPanel either in a JFrame, or if I'm really lazy, in a simple JOptionPane.