Develop Reference

populate DefaultTableModel after insert a row java

I am running a program with two frames. First one has a table, the second one has a form which allows adding a new user to the table. I think the problem is I didn't add a reference from the mainframe. I was trying different methods to refresh the mainframe programmatically, but it did not help so much. I read many articles on how to to it but I could find a solution. My table usually changes when I close my app and open it again. But I don't think is the right way to do it. I tried to delete elements from DefaultTableModel and populated jtable again, but did not get any results. Here is my code:
public Vector vector_jtable = new Vector();
public MainApp() {
initComponents();
Database b = new Database();
b.getAmountOfRows(getCount);
this.setLocationRelativeTo(null);
printResultDB();
}
//add function that is responsible for addding data to the table
public void postDataJtable() {
System.out.println("The vector is: " + vector_jtable);
Vector<String> header = new Vector<String>();
header.add("Number");
header.add("Name");
header.add("First Payment");
header.add("Next Payment");
header.add("Picture");
header.add("Phone");
header.add("Amount");
header.add("Age");
model = (DefaultTableModel)jTable2.getModel();
model.setDataVector(vector_jtable,header);
}
I created a vector that allows putting data from the second frame.
MainApp app;
public AddStudents(MainApp a) {
initComponents();
app = a;
this.setLocationRelativeTo(null);
jDateChooser1.setDateFormatString("yyyy-MM-dd");
jDateChooser2.setDateFormatString("yyyy-MM-dd");
}
After that, I push the button to send it out and update the mainframe, but nothing happened:
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
app.vector_jtable.add(name);
app.vector_jtable.add(first_p);
app.vector_jtable.add(next_p);
app.vector_jtable.add(picture);
app.vector_jtable.add(phone);
app.vector_jtable.add(amount);
app.vector_jtable.add(age);
app.postDataJtable();
My question. How to add a row in jtable and refresh it. I really stuck in this topic. I need your help.

Don't update the Vector.
When you want to change the data in the table you need to change the data in the TableModel.
You can use the addRow(...) method of the DefaultTableModel to add a new row of data.
So the basic logic is:
Vector<Object> row = new Vector<Object>();
row.add( someVariable1 );
row.add( someVariable2 );
...
modal.addRow( row ):
The model will then tell the table to repaint itself.
Edit:
There is no trick all you need is a reference to the model. Then you update the model.
Here is a simple example to prove the concept works:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.table.*;
public class SSCCE extends JPanel
{
private DefaultTableModel model;
SSCCE()
{
setLayout( new BorderLayout() );
model = new DefaultTableModel(0, 2);
JTable table = new JTable( model );
add(new JScrollPane( table ));
JButton button = new JButton( "Add Row" );
add(button, BorderLayout.PAGE_END);
button.addActionListener( new ActionListener()
{
#Override
public void actionPerformed(ActionEvent e)
{
Vector<Object> row = new Vector<Object>();
row.add( "" + model.getRowCount() );
row.add( new Date().toString() );
model.addRow( row );
}
});
}
private static void createAndShowGUI()
{
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new SSCCE());
frame.pack();
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args) throws Exception
{
java.awt.EventQueue.invokeLater( () -> createAndShowGUI() );
/*
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
*/
}
}
If it doesn't work for you then you need to debug your code. Maybe you have two "model" variables? Maybe you have to "table" variables. Maybe your code isn't even executed. Did you add any debug statements to the code to make sure it is executed.
We can't solve your problem only point you in the right direction.

You can try some aspects from this example below. The example has two JFrame's - one with a JTable and the other the data entry fields. When the data is entered and the "UpdateTable" button is pressed (in the data entry class) the table is updated.
The example uses java.util.Observer and Observable to achieve this functionality.
The class with table:
import java.awt.*;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import java.util.Observer;
import java.util.Observable;
public class TableUpdateTester implements Observer {
private JTable table;
private static final Object[] TABLE_COLUMNS = {"Book", "Author"};
private static final Object [][] TABLE_DATA = {
{"Book 1", "author 1"}, {"Book 2", "author 1"}
};
public static void main(String [] args) {
TableUpdateTester tester = new TableUpdateTester();
new DataEntryClass(tester);
}
public TableUpdateTester() {
JFrame frame = new JFrame("Table Update Tester");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(getTablePanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private JPanel getTablePanel() {
table = new JTable(new DefaultTableModel(TABLE_DATA, TABLE_COLUMNS));
JScrollPane scrollpane = new JScrollPane(table);
scrollpane.setPreferredSize(new Dimension(400, 150));
scrollpane.setViewportView(table);
JPanel panel = new JPanel();
panel.add(scrollpane);
return panel;
}
// This is Observer's override method.
#Override public void update(Observable o, Object arg) {
String [] data = (String []) arg;
System.out.println("Data recieving: " + java.util.Arrays.toString(data));
DefaultTableModel model = (DefaultTableModel) table.getModel();
model.addRow(data);
}
}
The data entry class:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Observable;
public class DataEntryClass {
public DataEntryClass(TableUpdateTester observer) {
final DataObservable observable = new DataObservable();
observable.addObserver(observer);
JLabel label = new JLabel("Book: ");
final JTextField text = new JTextField(15);
JLabel label2 = new JLabel("Author: ");
final JTextField text2 = new JTextField(15);
JButton button = new JButton("Update Table");
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String data1 = text.getText().isEmpty() ? "empty" : text.getText();
String data2 = text2.getText().isEmpty() ? "empty" : text2.getText();
String [] data = {data1, data2};
System.out.println("Data sent: " + java.util.Arrays.toString(data));
observable.changeData(data);
}
});
JPanel panel = new JPanel();
GridLayout grid = new GridLayout(3, 2);
panel.setLayout(grid);
panel.add(label);
panel.add(text);
panel.add(label2);
panel.add(text2);
panel.add(new JLabel(""));
panel.add(button);
JFrame frame = new JFrame();
frame.setTitle("Data Entry");
frame.add(panel);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
frame.pack();
}
}
class DataObservable extends Observable {
DataObservable() {
super();
}
void changeData(Object data) {
// the two methods of Observable class
setChanged();
notifyObservers(data);
}
}

Finally, I found a solution to my problem. I will post my code here.
The Mainframe. I know the app with two frames is not a good option, because it's hard to fix the problem and it usually takes a lot of time to debug it.
/**
* Create the application.
*/
public MainApp() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 689, 345);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
//add table in DefaultTableModel
model = new DefaultTableModel(0,2);
table = new JTable(model);
table.setBounds(58, 38, 524, 197);
frame.getContentPane().add(table);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setBounds(0, 0, 4, 4);
frame.getContentPane().add(scrollPane);
JButton btnNewButton = new JButton("Add");
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
//Call a second frame
//add reference for DefaultTableModel and send it to another frame
AddData frame = new AddData(model);
frame.setVisible(true);
}
});
btnNewButton.setBounds(239, 269, 117, 29);
frame.getContentPane().add(btnNewButton);
}
The second frame, that is responsible for adding a new row in a table.
/**
* Create the frame.
*/
public AddData(DefaultTableModel model) {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JDateChooser dateChooser = new JDateChooser();
dateChooser.setBounds(115, 71, 188, 41);
contentPane.add(dateChooser);
JButton btnNewButton = new JButton("Send");
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
//MainApp app = new MainApp();
Vector<Object> row = new Vector<Object>();
row.add(""+model.getRowCount());
row.add(dateChooser.getDate().toString());
model.addRow(row);
}
});
btnNewButton.setFont(new Font("Lucida Grande", Font.PLAIN, 20));
btnNewButton.setBounds(165, 192, 117, 41);
contentPane.add(btnNewButton);
}
I found my mistake. I did not send a link of DefaultTableModel into the second frame. That's why it was null every time. It was a really painful experience, but I learned from my mistakes. Thanks, everyone for your help. I really appriciate.

How to close JDialog and save the setting ?

Hi I'm working on a program and I faced a problem when I choose some settings from JDialog then click "ok", which is that the setting didn't save but come back to the original settings.
PS : I'm not English speaker so maybe you observe some mistakes in my text above.
picture
enter image description here
class DrawingSettingWindow extends JDialog {
public DrawingSettingWindow() {
this.setTitle("Drawing Setting Window");
this.setSize(550, 550);
this.setLocationRelativeTo(null);
this.setModal(true);
this.setLayout(new GridLayout(4, 1));
JLabel selectColorText = new JLabel("Select Drawing Color");
colorsList = new JComboBox(colors);
JPanel panel1 = new JPanel();
panel1.add(selectColorText);
panel1.add(colorsList);
add(panel1);
JLabel selectStyleText = new JLabel("Select Drawing Style");
JPanel panel2 = new JPanel();
normal = new JRadioButton("Normal");
normal.setSelected(true);
filled = new JRadioButton("Filled");
ButtonGroup bg = new ButtonGroup();
bg.add(normal);
bg.add(filled);
panel2.add(selectStyleText);
panel2.add(normal);
panel2.add(filled);
add(panel2);
JButton ok = new JButton("OK");
add(ok);
ok.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
});
this.pack();
this.setVisible(true);
}

The information is there, you just have to extract it from the dialog after the user is done using it. I would give the code above at least two new methods, one a public getColor() method that returns colorsList.getSelectedItem();, the color selection of the user (I'm not sure what type of object this is, so I can't show the method yet). Also another one that gets the user's filled setting, perhaps
public boolean getFilled() {
return filled.isSelected();
}
Since the dialog is modal, you'll know that the user has finished using it immediately after you set it visible in the calling code. And this is where you call the above methods to extract the data.
In the code below, I've shown this in this section: drawingSettings.setVisible(true);
// here you extract the data
Object color = drawingSettings.getColor();
boolean filled = drawingSettings.getFilled();
textArea.append("Color: " + color + "\n");
textArea.append("Filled: " + filled + "\n");
}
For example (see comments):
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
#SuppressWarnings("serial")
public class UseDrawingSettings extends JPanel {
private JTextArea textArea = new JTextArea(20, 40);
private DrawingSettingWindow drawingSettings;
public UseDrawingSettings() {
JPanel topPanel = new JPanel();
topPanel.add(new JButton(new ShowDrawSettings()));
setLayout(new BorderLayout());
add(new JScrollPane(textArea));
add(topPanel, BorderLayout.PAGE_START);
}
private class ShowDrawSettings extends AbstractAction {
public ShowDrawSettings() {
super("Get Drawing Settings");
}
#Override
public void actionPerformed(ActionEvent e) {
if (drawingSettings == null) {
Window win = SwingUtilities.getWindowAncestor(UseDrawingSettings.this);
drawingSettings = new DrawingSettingWindow(win);
}
drawingSettings.setVisible(true);
// here you extract the data
Object color = drawingSettings.getColor();
boolean filled = drawingSettings.getFilled();
textArea.append("Color: " + color + "\n");
textArea.append("Filled: " + filled + "\n");
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
private static void createAndShowGui() {
UseDrawingSettings mainPanel = new UseDrawingSettings();
JFrame frame = new JFrame("UseDrawingSettings");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
}
#SuppressWarnings("serial")
class DrawingSettingWindow extends JDialog {
private static final String TITLE = "Drawing Setting Window";
private JComboBox<String> colorsList;
private JRadioButton normal;
private JRadioButton filled;
// not sure what colors is, but I'll make it a String array for testing
private String[] colors = {"Red", "Orange", "Yellow", "Green", "Blue"};
public DrawingSettingWindow(Window win) {
super(win, TITLE, ModalityType.APPLICATION_MODAL);
// this.setTitle("Drawing Setting Window");
this.setSize(550, 550); // !! this is not recommended
this.setLocationRelativeTo(null);
this.setModal(true);
this.setLayout(new GridLayout(4, 1));
JLabel selectColorText = new JLabel("Select Drawing Color");
colorsList = new JComboBox(colors);
JPanel panel1 = new JPanel();
panel1.add(selectColorText);
panel1.add(colorsList);
add(panel1);
JLabel selectStyleText = new JLabel("Select Drawing Style");
JPanel panel2 = new JPanel();
normal = new JRadioButton("Normal");
normal.setSelected(true);
filled = new JRadioButton("Filled");
ButtonGroup bg = new ButtonGroup();
bg.add(normal);
bg.add(filled);
panel2.add(selectStyleText);
panel2.add(normal);
panel2.add(filled);
add(panel2);
JButton ok = new JButton("OK");
add(ok);
ok.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
});
this.pack();
// this.setVisible(true); // this should be the calling code's responsibility
}
public Object getColor() {
return colorsList.getSelectedItem();
}
public boolean getFilled() {
return filled.isSelected();
}
public static void main(String[] args) {
JFrame frame = new JFrame("Foo");
}
}
Side notes:
I've changed your class's constructor to accept a Window parameter, the base class for JFrame, JDialog, and such, and have added a call to the super's constructor. This way, the dialog is a true child window of the calling code (or you can pass in null if you want it not to be).
I recommend not making the dialog visible within its constructor. It is the calling code's responsibility for doing this, and there are instances where the calling code will wish to not make the dialog visible after creating it, for example if it wanted to attach a PropertyChangeListener to it before making it visible. This is most important for modal dialogs, but is just good programming practice.
I didn't know the type of objects held by your combo box, and so made an array of String for demonstration purposes.

How can I get the contents of my GUI to look a certain way? (Java)

So, I'm brand spankin' new to programming, so thanks in advance for your help. I'm trying to put this base 2 to base 10/base 10 to base 2 calculator I have made into a GUI. For the life of me I can't figure out how to nicely format it. I'm trying to make it look like the following: The two radio buttons on top, the input textfield bellow those, the convert button bellow that, the output field bellow that, and the clear button bellow that. Any ideas on how I can accomplish this?
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.GridLayout;
import java.awt.BorderLayout;
import java.awt.Color;
import javax.swing.*;
#SuppressWarnings("serial")
public class GUI extends JFrame implements ActionListener
{
private JTextField input;
private JTextField output;
private JRadioButton base2Button;
private JRadioButton base10Button;
private JButton convert;
private JButton clear;
private Container canvas = getContentPane();
private Color GRAY;
public GUI()
{
this.setTitle("Base 10-2 calc");
this.setLayout(new FlowLayout(FlowLayout.LEFT));
//this.setLayout(new GridLayout(2,2));
base2Button = new JRadioButton( "Convert to base 2");
base10Button = new JRadioButton( "Convert to base 10");
ButtonGroup radioGroup = new ButtonGroup();
radioGroup.add(base2Button);
radioGroup.add(base10Button);
JPanel radioButtonsPanel = new JPanel();
radioButtonsPanel.setLayout( new FlowLayout(FlowLayout.LEFT) );
radioButtonsPanel.add(base2Button);
radioButtonsPanel.add(base10Button);
canvas.add(radioButtonsPanel);
base2Button.setSelected( true );
base10Button.setSelected( true );
input = new JTextField(18);
//input = new JFormattedTextField(20);
canvas.add(input);
output = new JTextField(18);
//output = new JFormattedTextField(20);
canvas.add(output);
convert = new JButton("Convert!");
convert.addActionListener(this);
canvas.add(convert);
clear = new JButton("Clear");
clear.addActionListener(this);
canvas.add(clear);
output.setBackground(GRAY);
output.setEditable(false);
this.setSize(300, 200);
this.setVisible(true);
this.setLocation(99, 101);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String[] args)
{
GUI app = new GUI();
app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
#Override
public void actionPerformed(ActionEvent e)
{
String s = e.getActionCommand();
if(s.equals("Convert!"))
{
String numS = input.getText();
int numI = Integer.parseInt(numS);
if(base2Button.isSelected())
{
output.setText(Integer.toBinaryString(Integer.valueOf(numI)));
}
if(base10Button.isSelected())
{
output.setText("" + Integer.valueOf(numS,2));
}
}
if(s.equals("Clear"))
{
input.setText("");
output.setText("");
}
}
}

For a simple layout, you could use a GridLayout with one column and then use a bunch of child panels with FlowLayout which align the components based on the available space in a single row. If you want more control, I'd suggest learning about the GridBagLayout manager which is a more flexible version of GridLayout.
public class ExampleGUI {
public ExampleGUI() {
init();
}
private void init() {
JFrame frame = new JFrame();
// Set the frame's layout to a GridLayout with one column
frame.setLayout(new GridLayout(0, 1));
frame.setPreferredSize(new Dimension(300, 300));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Child panels, each with FlowLayout(), which aligns the components
// in a single row, until there's no more space
JPanel radioButtonPanel = new JPanel(new FlowLayout());
JRadioButton button1 = new JRadioButton("Option 1");
JRadioButton button2 = new JRadioButton("Option 2");
radioButtonPanel.add(button1);
radioButtonPanel.add(button2);
JPanel inputPanel = new JPanel(new FlowLayout());
JLabel inputLabel = new JLabel("Input: ");
JTextField textField1 = new JTextField(15);
inputPanel.add(inputLabel);
inputPanel.add(textField1);
JPanel convertPanel = new JPanel(new FlowLayout());
JButton convertButton = new JButton("Convert");
convertPanel.add(convertButton);
JPanel outputPanel = new JPanel(new FlowLayout());
JLabel outputLabel = new JLabel("Output: ");
JTextField textField2 = new JTextField(15);
outputPanel.add(outputLabel);
outputPanel.add(textField2);
// Add the child panels to the frame, in order, which all get placed
// in a single column
frame.add(radioButtonPanel);
frame.add(inputPanel);
frame.add(convertPanel);
frame.add(outputPanel);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
ExampleGUI example = new ExampleGUI();
}
}
The end result:

Adding elements (i.e. JLabels) outside of the set layout

As part of a project we've got to have 9 boxes, here I've just implemented alternating colors as an example in place of the images we should be using. But whilst I want these 9 JLabels in this grid layout (3,3), I also want to have a message at the top (a JLabel) that I can just centralize, like a welcoming message as well as having around four JButtons underneath? Can somebody please point me in the right direction as to how to achieve this?
Thank you!
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class HomeController extends JPanel implements MouseListener
{
HomeController()
{
setLayout(new GridLayout(3,3));
JLabel apl1 = new JLabel("");
apl1.setBackground(Color.WHITE);
apl1.setOpaque(true);
this.add(apl1);
JLabel apl2 = new JLabel("");
apl2.setBackground(Color.BLACK);
apl2.setOpaque(true);
this.add(apl2);
JLabel apl3 = new JLabel("");
apl3.setBackground(Color.WHITE);
apl3.setOpaque(true);
this.add(apl3);
JLabel apl4 = new JLabel("");
apl4.setBackground(Color.BLACK);
apl4.setOpaque(true);
this.add(apl4);
JLabel apl5 = new JLabel("");
apl5.setBackground(Color.WHITE);
apl5.setOpaque(true);
this.add(apl5);
JLabel apl6 = new JLabel("");
apl6.setBackground(Color.BLACK);
apl6.setOpaque(true);
this.add(apl6);
JLabel apl7 = new JLabel("");
apl7.setBackground(Color.WHITE);
apl7.setOpaque(true);
this.add(apl7);
JLabel apl8 = new JLabel("");
apl8.setBackground(Color.BLACK);
apl8.setOpaque(true);
this.add(apl8);
JLabel apl9 = new JLabel("");
apl9.setBackground(Color.WHITE);
apl9.setOpaque(true);
this.add(apl9);
JLabel message = new JLabel("hello world");
this.add(message);
}
}

You can combine multiple panels with different layouts. For details take a look at A Visual Guide to Layout Managers.
For example, default layout of JFrame is BorderLayout. Using BorderLayout, you can place the title at BorderLayout.NORTH, panel with buttons at BorderLayout.SOUTH and panel with grid of labels at BorderLayout.CENTER. Each panel may have its own more complex layout. For example, grid of labels is using GridLayout, and buttons panel is using FlowLayout.
Here is a very simple example based on the posted code that demonstrates this approach:
import java.awt.*;
import javax.swing.*;
public class TestGrid {
public TestGrid() {
final JFrame frame = new JFrame("Grid");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel mainPanel = new JPanel(new GridLayout(3, 3));
for (int idx = 0; idx < 9; idx++) {
JLabel label = new JLabel();
label.setBackground(idx % 2 == 0 ? Color.WHITE : Color.BLACK);
label.setOpaque(true);
mainPanel.add(label);
}
mainPanel.setPreferredSize(new Dimension(200, 200));
frame.add(mainPanel, BorderLayout.CENTER);
frame.add(new JLabel("Title", JLabel.CENTER), BorderLayout.NORTH);
JPanel buttonsPanel = new JPanel();
buttonsPanel.add(new JButton("Start"));
buttonsPanel.add(new JButton("Stop"));
frame.add(buttonsPanel, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception e) {
e.printStackTrace();
}
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestGrid();
}
});
}
}

How to add JTable in JPanel with null layout?

I want to add JTable into JPanel whose layout is null. JPanel contains other components. I have to add JTable at proper position.

Nested/Combination Layout Example
The Java Tutorial has comprehensive information on using layout managers. See the Laying Out Components Within a Container lesson for further details.
One aspect of layouts that is not covered well by the tutorial is that of nested layouts, putting one layout inside another to get complex effects.
The following code puts a variety of components into a frame to demonstrate how to use nested layouts. All the layouts that are explicitly set are shown as a titled-border for the panel on which they are used.
Notable aspects of the code are:
There is a combo-box to change PLAF (Pluggable Look and Feel) at run-time.
The GUI is expandable to the user's need.
The image in the bottom of the split-pane is centered in the scroll-pane.
The label instances on the left are dynamically added using the button.
Nimbus PLAF
NestedLayoutExample.java
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import javax.swing.border.TitledBorder;
/** A short example of a nested layout that can change PLAF at runtime.
The TitledBorder of each JPanel shows the layouts explicitly set.
#author Andrew Thompson
#version 2011-04-12 */
class NestedLayoutExample {
public static void main(String[] args) {
Runnable r = new Runnable() {
public void run() {
final JFrame frame = new JFrame("Nested Layout Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel gui = new JPanel(new BorderLayout(5,5));
gui.setBorder( new TitledBorder("BorderLayout(5,5)") );
//JToolBar tb = new JToolBar();
JPanel plafComponents = new JPanel(
new FlowLayout(FlowLayout.RIGHT, 3,3));
plafComponents.setBorder(
new TitledBorder("FlowLayout(FlowLayout.RIGHT, 3,3)") );
final UIManager.LookAndFeelInfo[] plafInfos =
UIManager.getInstalledLookAndFeels();
String[] plafNames = new String[plafInfos.length];
for (int ii=0; ii<plafInfos.length; ii++) {
plafNames[ii] = plafInfos[ii].getName();
}
final JComboBox plafChooser = new JComboBox(plafNames);
plafComponents.add(plafChooser);
final JCheckBox pack = new JCheckBox("Pack on PLAF change", true);
plafComponents.add(pack);
plafChooser.addActionListener( new ActionListener(){
public void actionPerformed(ActionEvent ae) {
int index = plafChooser.getSelectedIndex();
try {
UIManager.setLookAndFeel(
plafInfos[index].getClassName() );
SwingUtilities.updateComponentTreeUI(frame);
if (pack.isSelected()) {
frame.pack();
frame.setMinimumSize(frame.getSize());
}
} catch(Exception e) {
e.printStackTrace();
}
}
} );
gui.add(plafComponents, BorderLayout.NORTH);
JPanel dynamicLabels = new JPanel(new BorderLayout(4,4));
dynamicLabels.setBorder(
new TitledBorder("BorderLayout(4,4)") );
gui.add(dynamicLabels, BorderLayout.WEST);
final JPanel labels = new JPanel(new GridLayout(0,2,3,3));
labels.setBorder(
new TitledBorder("GridLayout(0,2,3,3)") );
JButton addNew = new JButton("Add Another Label");
dynamicLabels.add( addNew, BorderLayout.NORTH );
addNew.addActionListener( new ActionListener(){
private int labelCount = 0;
public void actionPerformed(ActionEvent ae) {
labels.add( new JLabel("Label " + ++labelCount) );
frame.validate();
}
} );
dynamicLabels.add( new JScrollPane(labels), BorderLayout.CENTER );
String[] header = {"Name", "Value"};
String[] a = new String[0];
String[] names = System.getProperties().
stringPropertyNames().toArray(a);
String[][] data = new String[names.length][2];
for (int ii=0; ii<names.length; ii++) {
data[ii][0] = names[ii];
data[ii][1] = System.getProperty(names[ii]);
}
DefaultTableModel model = new DefaultTableModel(data, header);
JTable table = new JTable(model);
try {
// 1.6+
table.setAutoCreateRowSorter(true);
} catch(Exception continuewithNoSort) {
}
JScrollPane tableScroll = new JScrollPane(table);
Dimension tablePreferred = tableScroll.getPreferredSize();
tableScroll.setPreferredSize(
new Dimension(tablePreferred.width, tablePreferred.height/3) );
JPanel imagePanel = new JPanel(new GridBagLayout());
imagePanel.setBorder(
new TitledBorder("GridBagLayout()") );
BufferedImage bi = new BufferedImage(
200,200,BufferedImage.TYPE_INT_ARGB);
Graphics2D g = bi.createGraphics();
GradientPaint gp = new GradientPaint(
20f,20f,Color.red, 180f,180f,Color.yellow);
g.setPaint(gp);
g.fillRect(0,0,200,200);
ImageIcon ii = new ImageIcon(bi);
JLabel imageLabel = new JLabel(ii);
imagePanel.add( imageLabel, null );
JSplitPane splitPane = new JSplitPane(
JSplitPane.VERTICAL_SPLIT,
tableScroll,
new JScrollPane(imagePanel));
gui.add( splitPane, BorderLayout.CENTER );
frame.setContentPane(gui);
frame.pack();
frame.setLocationRelativeTo(null);
try {
// 1.6+
frame.setLocationByPlatform(true);
frame.setMinimumSize(frame.getSize());
} catch(Throwable ignoreAndContinue) {
}
frame.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}
Other Screen Shots
Windows PLAF
Mac OS X Aqua PLAF
Ubuntu GTK+ PLAF

Don't use a null layout. Learn to use LayoutManagers:
http://download.oracle.com/javase/tutorial/uiswing/layout/using.html
LayoutManagers allow you to properly handle things window resizing or dynamic component counts. They might seem intimidating at first, but they are worth the effort to learn.

As I can remember, the null layout means an absolute position so it will be pretty hard you to count the X point for your JTable left upper corner location. But if you just want to have all panel components one by one you can use FlowLayout() manager as
JPanel panel=new JPanel(new FlowLayout());
panel.add(new aComponent());
panel.add(new bComponent());
panel.add(new JTable());
or if you need to fill the panel you should use GridLayout() as...
int x=2,y=2;
JPanel panel=new JPanel(new GridLayout(y,x));
panel.add(new aComponent());
panel.add(new bComponent());
panel.add(new JTable());
Good luck

If you are using null layout manager you always need to set the bounds of a component.
That is the problem in your case.
You should do what everyone suggest here and go and use some layout manager believe they save time.
Go and check out the tutorial in #jzd's post.
Enjoy, Boro.

JTable should be added into the JScrollPane which actually should be added into the JPanel.
The JPanel should have some layout manager.
If you don't care about the precision of components size you can use pure BorderLayout and combine it with FlowLayout and GridLayout. if you need precision - use jgoodies FormLayout.
The FormLayout is really tricky one, but you can play a little with WindowBuilder (which is embedded into Eclipse) and a look at the code it generates. It may look complicated but it is just an ignorance.
Good luck.

First, you should seriously consider other Layout managers, for example the BorderLayoutManager (new JPanel(new BorderLayout())) is a good start.
Also when designing your dialog, remember that you can and should nest your layouts: one JPanel inside another JPanel (e.g. a GridLayout inside a BorderLayout). Please note: a 'good' dialog should resize properly, so that if the user resizes your Frame, you want to automatically extend your information objects such as your table, and not show large areas of JPanel background. That's something you cannot achieve with a NullLayout.
But there are probably cases - somewhere in this big world - where a NullLayout is just the thing. So here's an example:
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
public class JTableInNullLayout
{
public static void main(String[] argv) throws Exception {
DefaultTableModel model = new DefaultTableModel(
new String[][] { { "a", "123"} , {"b", "456"} },
new String[] { "name", "value" } );
JTable t = new JTable(model);
JPanel panel = new JPanel(null);
JScrollPane scroll = new JScrollPane(t);
scroll.setBounds( 0, 20, 150, 100 ); // x, y, width, height
panel.add(scroll);
JFrame frame = new JFrame();
frame.add(panel);
frame.setPreferredSize( new Dimension(200,200));
frame.pack();
frame.setVisible(true);
}
}

When a component have a "null" layout, you have to manage the layout by yourself, that means you have to calculate the dimensions and locations for the children of the component to decide where they are drawn. Quite tedious unless it is absolutely necessary.
If you really want that fine-grained control, maybe try GridBagLayout first before going mudding with the UI arrangement.

JPanel panel = new JPanel();
JTable table = new JTable(rowData, colData);
JScrollPane scrollPane = new JScrollPane(table);
panel.add(scrollPane, BorderLayout.CENTER);
panel.setSize(800, 150);
panel.add(table);
panel.setLocationRelativeTo(null);
panel.setVisible(true);
Hope this helps.

JFrame frame = new JFrame("Sample Frame");
frame.setSize(600, 600);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
DefaultTableModel dfm = new DefaultTableModel(data, columnNames);
JTable table = new JTable(dfm);
JScrollPane scrollPane = new JScrollPane(table);
panel.add(scrollPane);
frame.add(panel);
frame.setVisible(true);
table model depends on your requirement

this.setTitle("Sample");
JPanel p = new JPanel(new BorderLayout());
WindowEvent we = new WindowEvent(this, WindowEvent.WINDOW_CLOSED);
this.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent we) {
System.exit(0);
}
});
// Create columns names
String columnNames[] = { "FirstCol", "SecondCol",
"ThirdCol", "FourthCol" };
dataModel = new DefaultTableModel();
for (int col = 0; col < columnNames.length; col++) {
dataModel.addColumn(columnNames[col]);
}
// Create a new table instance
table = new JTable(dataModel);
table.setPreferredScrollableViewportSize(new Dimension(200, 120));
table.setFillsViewportHeight(true);
table.setShowGrid(true);
table.setAutoscrolls(true);
// Add the table to a scrolling pane
scrollPane = new JScrollPane(table,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.setPreferredSize(new Dimension(700, 700));
JPanel jpResultPanel = new JPanel();
jpResultPanel.setBorder(BorderFactory.createTitledBorder(
BorderFactory.createEtchedBorder(), "Result",
TitledBorder.CENTER, TitledBorder.TOP));
jpResultPanel.add(scrollPane);
add(jpResultPanel);
pack();
setSize(720, 720);
setVisible(true);
Try this.

You can make use of the following code. To add JTable to JPanel.
JPanel panel = new JPanel();
this.setContentPane(panel);
panel.setLayout(null);
String data[][] = {{"1.", "ABC"}, {"2.", "DEF"}, {"3.", "GHI" }};
String col[] = {"Sr. No", "Name"};
JTable table = new JTable(data,col);
table.setBounds(100, 100, 100, 80);
panel.add(table);
setVisible(true);
setSize(300,300);