Hi everyone,

                 I am trying to save the contents the of the jtable
together with all its fonts and everything else. The program compiles
without any errors but When i try to save the contents of the JTable an
exception is thrown in the tablesaveas method in the below method

Please note that i am saving the jtable as an object. I am providing
the below runnable example so you guys can compile and run and see what
i mean.

Here is the code

import java.awt.*;
import java.io.*;
import java.util.*;
import java.awt.print.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;

public class JTablesui implements ActionListener, ItemListener

{

    JFrame fr = new JFrame ("Frame");
    JDialog Dialog1 = new JDialog (fr, "Row Height");

    JLabel Label1 = new JLabel("Label1                       ",
SwingConstants.RIGHT);
    JLabel Label2 = new JLabel("                             ",
SwingConstants.LEFT);
    JLabel Label3 = new JLabel("Enter table row height in pixels");

    JButton Button6 = new JButton("Save As");
    JButton Button19 = new JButton("Set Row Height");
    JButton Button20 = new JButton("Set Height");
    JButton Button21 = new JButton("Close");
    JButton Button22 = new JButton("Foreground Color For Cells");

    JTextField TextField1 = new JTextField("", 10);
    JTextField TextField2 = new JTextField("", 20);
    JTextField TextField3 = new JTextField("", 10);

    JComboBox ComboBox1;
    JComboBox ComboBox2 = new JComboBox();

    //The below command line sets the model for the JTable which
    //has two arguments as explained below
    //The first argument specifies the number of rows for the JTable to
display upon
    //it's initialization
    //The second argument specifies the number of columns for the JTable
to display upon
    //it's initialization

    DefaultTableModel TableModel1 = new DefaultTableModel(5, 10);

    //The below command line sets the table model to the JTable

    JTable Table1 = new JTable(TableModel1);

    JScrollPane ScrollPane1 = new JScrollPane(Table1,
ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
    ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);

    JFileChooser FileChooser1 = new JFileChooser();

    JColorChooser ColorChooser3 = new JColorChooser();

    Color Color3;

    Dimension Size1 = new Dimension();

    int FontSize = 12;
    String FontFamily = "Arial";

    String SF = "";

    public void initialize ()
    {
        Container pane = fr.getContentPane();
        pane.setLayout(new FlowLayout());
        fr.setSize(250,300);
        fr.setLocation(300,300);
        fr.setBackground(Color.lightGray);
        //The below command line must be set to false so that user
        //resizing is allowed

        Table1.setAutoCreateColumnsFromModel(false);
        Size1.width = 350;
        Size1.height = 250;
        ScrollPane1.setPreferredSize(Size1);
        Table1.setModel(TableModel1);
        //The below command line must be set to JTable.AUTO_RESIZE_OFF so
that user
        //resizing is allowed

        Table1.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
        pane.add(ScrollPane1);
        pane.add(Button6);
        pane.add(Button19);
        pane.add(Button22);
        combofontfamilyinitialize();
        pane.add(ComboBox1);
        combofontsizeinitialize();
        pane.add(ComboBox2);
        pane.add(Label1);

        // Use the JAVA constant JFrame.HIDE_ON_CLOSE for subsequent forms in
multi form
        // applications

        fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Button6.addActionListener(this);
        Button19.addActionListener(this);
        Button22.addActionListener(this);
        ComboBox1.addItemListener(this);
        ComboBox2.addItemListener(this);
        fr.pack();
        fr.setVisible(true);
    }

    public void combofontfamilyinitialize ()
    {
        //This function fills the combo box with the system available font
families

        GraphicsEnvironment ge1 =
GraphicsEnvironment.getLocalGraphicsEnvironment();
        String[] k = ge1.getAvailableFontFamilyNames();
        ComboBox1= new JComboBox(k);
    }

    public void combofontsizeinitialize ()
    {
        //This function fills the combo box with font sizes

        ComboBox2.addItem("8");
        ComboBox2.addItem("9");
        ComboBox2.addItem("10");
        ComboBox2.addItem("11");
        ComboBox2.addItem("12");
        ComboBox2.addItem("14");
        ComboBox2.addItem("16");
        ComboBox2.addItem("18");
        ComboBox2.addItem("20");
        ComboBox2.addItem("22");
        ComboBox2.addItem("24");
        ComboBox2.addItem("26");
        ComboBox2.addItem("28");
        ComboBox2.addItem("36");
        ComboBox2.addItem("48");
        ComboBox2.addItem("72");
    }

    public void initializedialog1 ()
    {
        Container pane1 = Dialog1.getContentPane();
        pane1.setLayout(new BoxLayout(pane1, BoxLayout.Y_AXIS));
        Dialog1.setSize(250,300);
        Dialog1.setLocation(300,300);
        Dialog1.setBackground(Color.lightGray);
        pane1.add(Label3);
        pane1.add(TextField3);
        pane1.add(Button20);
        pane1.add(Button21);

        //Use the JAVA constant JDialog.HIDE_ON_CLOSE for subsequent forms in
multi form
        //applications

        Dialog1.setDefaultCloseOperation(JDialog.HIDE_ON_CLOSE);
        Button20.addActionListener(this);
        Button21.addActionListener(this);
        Dialog1.pack();
        Dialog1.setVisible(true);
    }

    public void tablesaveas ()
    {
        //This function saves the model of the table to disk using the user
        //specified file name

        //This is the function in which the exception is thrown

        if(FileChooser1.showSaveDialog(fr) != JFileChooser.APPROVE_OPTION)
        {
            return;
        }

        try
        {
            File f = FileChooser1.getSelectedFile();
            SF = (f.toString() + ".DAT");
            FileOutputStream fStream = new FileOutputStream(SF);
            ObjectOutput stream = new ObjectOutputStream(fStream);

            //The below two command lines saves the table model and table column
data
            //as an object using the user specified file name
            stream.writeObject(Table1.getModel());
            stream.writeObject(Table1.getColumnModel());
            stream.writeObject(Table1.getFont());
            stream.writeObject(Table1.getForeground());
            stream.writeObject(TextField3.getText());
            stream.writeObject(Label2);
            stream.flush();
            stream.close();
            fStream.close();
        }

        catch (Exception e)
        {
            Label1.setText("A table saving error has occurred");
        }

    }

    public void actionPerformed(ActionEvent event)
    {
        JComponent b = (JComponent)event.getSource();
        int d, d1;
        String str3;

        if(b == Button6)
        {
            //This is the function in which the exception is thrown

            tablesaveas();
        }

        else if(b == Button19)
        {
            d = Table1.getRowHeight();
            str3 = Integer.toString(d);
            TextField3.setText(str3);
            initializedialog1();
        }

        else if(b == Button20)
        {
            str3 = TextField3.getText();
            d = Integer.parseInt(str3);
            Table1.setRowHeight(d);
        }

        else if(b == Button21)
        {
            Dialog1.setVisible(false);
        }

        else if(b == Button22)
        {
            Color3 = ColorChooser3.showDialog(fr, "Color Chooser", Color.black);
            //The below command line test to see if the Ok button or the Cancel
button
            //was clicked on the JColorChooser as if no color is selected the
JColorChooser
            //simply returns a null

            if(Color3 != null)
            {
                Table1.editCellAt(0,0);
                TextField1 = (JTextField)Table1.getEditorComponent();

                if(TextField1 != null)
                {
                    TextField1.setForeground(Color3);
                }

                Table1.setSelectionForeground(Color3);
                Table1.setForeground(Color3);

            }

        }

    }

    public void itemStateChanged(ItemEvent event)
    {
        JComponent c = (JComponent)event.getSource();

        if(c == ComboBox1)
        {
            Table1.editCellAt(0,0);
            FontFamily = (String)ComboBox1.getSelectedItem();
            Font Font1 = new Font(FontFamily, Font.PLAIN, FontSize);
            TextField1 = (JTextField)Table1.getEditorComponent();

            if(TextField1 != null)
            {
                TextField1.setFont(Font1);
            }

            Table1.setFont(Font1);
        }

        else if(c == ComboBox2)
        {
            String h = (String)ComboBox2.getSelectedItem();
            FontSize = Integer.parseInt(h);
            Table1.editCellAt(0,0);
            Font Font2 = new Font(FontFamily, Font.PLAIN, FontSize);
            TextField1 = (JTextField)Table1.getEditorComponent();

            if(TextField1 != null)
            {
                TextField1.setFont(Font2);
            }

            Table1.setFont(Font2);
        }

    }
    public static void main(String args[])
    {
        JTablesui a = new JTablesui();
        a.initialize();
    }
}

This is the exception that is thrown. The exception does not seem to be
thrown from my own code.

Here is the exception thrown

java.lang.NullPointerException
    at
javax.swing.plaf.basic.BasicTableUI.getPreferredSize(BasicTableUI.java:908)
    at javax.swing.JComponent.getPreferredSize(JComponent.java:1275)
    at
javax.swing.ScrollPaneLayout.layoutContainer(ScrollPaneLayout.java:769)
    at java.awt.Container.layout(Container.java:1020)
    at java.awt.Container.doLayout(Container.java:1010)
    at java.awt.Container.validateTree(Cojava.lang.NullPointerException
    at javax.swing.plaf.basic.BasicTableUI.paint(BasicTableUI.java:939)
    at javax.swing.plaf.ComponentUI.update(ComponentUI.java:142)
    at javax.swing.JComponent.paintComponent(JComponent.java:541)
    at javax.swing.JComponent.paint(JComponent.java:808)
    at javax.swing.JComponent.paintChildren(JComponent.java:647)
    at javax.swing.JComponent.paint(JComponent.java:817)
    at javax.swing.JViewport.paint(JViewport.java:722)
    at javax.swing.JComponent.paintChildren(JComponent.java:647)
    at javax.swing.JComponent.paint(JComponent.java:817)
    at javax.swing.JComponent.paintChildren(JComponent.java:647)
    at javax.swing.JComponent.paint(JComponent.java:817)
    at javax.swing.JComponent.paintChildren(JComponent.java:647)
    at javax.swing.JComponent.paint(JComponent.java:817)
    at javax.swing.JLayeredPane.paint(JLayeredPane.java:557)
    at javax.swing.JComponent.paintChildren(JComponent.java:647)
    at
javax.swing.JComponent.paintWithOffscreenBuffer(JComponent.java:4794)
    at javax.swing.JComponent.paintDoubleBuffered(JComponent.java:4740)
    at javax.swing.JComponent.paint(JComponent.java:798)
    at
java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
    at
sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
    at
sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
    at java.awt.Container.paint(Container.java:1312)
    at sun.awt.RepaintArea.paint(RepaintArea.java:177)
    at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:260)
    at java.awt.Component.dispatchEventImpl(Component.java:3678)
    at java.awt.Container.dispatchEventImpl(Container.java:1627)
    at java.awt.Window.dispatchEventImpl(Window.java:1606)
    at java.awt.Component.dispatchEvent(Component.java:3477)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
    at
java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
    at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
    at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
    at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

As you can see from my above code in the tablesaveas method i am saving

six objects but if i change the tablesaveas method to this(see the
below code) the table is saved without any problems

public void tablesaveas ()
    {
        //This function saves the model of the table to disk using the user
        //specified file name

        //This is the function in which the exception is thrown

        if(FileChooser1.showSaveDialog(fr) != JFileChooser.APPROVE_OPTION)
        {
            return;
        }

        try
        {
            File f = FileChooser1.getSelectedFile();
            SF = (f.toString() + ".DAT");
            FileOutputStream fStream = new FileOutputStream(SF);
            ObjectOutput stream = new ObjectOutputStream(fStream);

            //The below two command lines saves the table model and table column
data
            //as an object using the user specified file name
            stream.writeObject(Table1.getModel());
            stream.writeObject(Table1.getColumnModel());
            stream.flush();
            stream.close();
            fStream.close();
        }

        catch (Exception e)
        {
            Label1.setText("A table saving error has occurred");
        }

    }

The only difference as you can see is that i am writing two objects
instead of six and i don't really know what's wrong . I don't know if
this is a bug in Java or am i missing something.

I am using JDK 1.4.2_04

I hope someone can help me with this problem

Any help is greatly appreciated

Thank You

Yours Sincerely

Richard West