Why is HeadlessException explicitly thrown in AWT and swing?

Hi there,
I just noticed that HeadlessException is explicitly thrown in some of the constructors in AWT and swing components since J2SE 1.4.
Given that it's a RuntimeException (unchecked) it doesn't need to be included in the throws clause of the method or constructor.
There also seems to be inconsistent application of it and inconsistent documentation in the javadoc comments.
Is this a work in progress or did some refactoring go wrong?

Most probably IE security settings preventing the js file to be executed. Replied in your other post:
Unable to get property 'style' of undefined or null reference in sp.ui.dialog.debug.js
Thanks,
Sohel Rana
http://ranaictiu-technicalblog.blogspot.com

Similar Messages

Lighter Java GUI than awt and swing?

I had recently came across a company website (http://www.bambookit.com) where they developed a java gui library without using awt and swing (seems to what they claim). And on top of that it uses xml to generate the gui components (they call widgets) and the whole library size is only 95kb and supports java 1.1.x and above. Their demos on the applets loads super fast, never know/experience that java applets can actually be this quick. But this confuses me, how is it possible to develop a gui alternative to awt with the basic java classes and no dependency on awt? But since the applets are awt based, it means that they must have some dependencies.
This is an extract from their website (that it seemed they did not use awt)
"Java has a fundamental flaw in its paint thread that made it very difficult to build extremely large applications without getting severe performance and resource penalties (This affects both AWT and Swing based applications). It�s main repaint queue\thread when assigning paint regions to various controls uses the Graphics objects to �clip� them. On a Sun Solaris machine this does not cause any problems, however on a windows machine each Graphics object consumes a system resource/handle, (a limit of around 16,000 exists on Win 95 and Win 98 machines). Each Bitmap image, each font object, each icon consumes a single system resource or handle. If a full repaint is performed on an application containing 1000 controls, it would consume at LEAST 1000 system resource handles. If the application was updated many times a second, lets say 10 times a second, then that equates to 10,000 handles a second. This is not taking into account labels within controls, the various fonts styles and sizes created, the various images that get loaded. This could easily exceed 20,000 system resource requests a second. Bambookit on the other hand utilizes the clip routines and passes along a SINGLE Graphics objects to all its various controls. This alone is a HUGE savings in system resources and performance."
Two questions came to my mind:
1) Is it possible to build applet gui without using awt and swing in java? If so the only way to do is to use JNI calls?
2) Am I wrong in interpreting www.bambookit.com's message that they are not using awt?
Any comments about this?
Regards,
Stanly

They use AWT as basis for their drawing-layer, as any other lightweight toolkits too.
If you just want a very fast & light alternative to swing/awt have a look at www.lwvcl.com !
I use it for a large applet-applikation that has to be java-1.1 compatible. It was a horor when using AWT which was implemented different over all JVMs available and very slow (although native widgets were used).
With lwvcl (which has only 150kB!) I can use state of the art applets that work very fast on modern jvms like 1.4, give me the ability to compile my applikation to native code using GCJ (using the swt-prt of the library) or distribute it to old-school 1.1 browser where it also runs quite fine...
Its free for GPL and very cheap for commercial use.
lg Clemens

Database Connection to AWT and Swings

How do we provide database connection to AWT and swing components?
Is their any possibility to create database connection?
Thanks in advance

Just create an independent DAO class which does all the database/JDBC tasks.
Then use this DAO class as you use every other class in your AWT/Swing application.

Differences between awt and swing

Ive written the following code, however Ive implemented the gui in awt rather then swing. Ive been told it hs too be in swing. What is the difference between swing and awt what will I need to change in my program so that its done using swing rather then the awt? Heres the code:
// pp.java
// Grant Brown
// 22/02/02
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
// =========================================================
// Class: pp
// This class drives the customer manager. It contains the
// main method which gets called as soon as this application
// begins to run.
// =========================================================
class pp extends Frame implements ActionListener
// Container of customer objects
private Vector customers = new Vector (100);
// List of names component. (Must specify java.awt in
// front of List to distinguish the List class in the
// java.awt package from the List class in the java.util
// package.)
private java.awt.List names = new java.awt.List ();
// Delete and update button components.
private Button delete;
private Button update;
// Default constructor.
public pp ()
// Assign "Paper Round Manager" to title bar of frame window.
super ("Paper Round Manager");
// Add a listener that responds to window closing
// events. When this event occurs (by clicking on the
// close box in the title bar), save customers and exit.
addWindowListener (new WindowAdapter ()
public void windowClosing
(WindowEvent e)
saveCustomers ();
System.exit (0);
// Place an empty label in the north part of the frame
// window. This is done to correct an AWT positioning
// problem.
Label l = new Label ();
add ("North", l);
// Place the names component in the center part of the
// frame window.
add ("Center", names);
// Create a panel object to hold four buttons.
Panel p = new Panel ();
Button b;
// Add an Insert button to the Panel object and register
// the current pp object as a listener for button events.
p.add (b = new Button ("Insert"));
b.addActionListener (this);
// Add a Delete button to the Panel object and register
// the current pp object as a listener for button events.
p.add (delete = new Button ("Delete"));
delete.addActionListener (this);
// The Delete button should be disabled until there is at
// least one customer to delete.
delete.setEnabled (false);
// Add an Update button to the Panel object and register
// the current pp object as a listener for button events.
p.add (update = new Button ("Update"));
update.addActionListener (this);
// The Update button should be disabled until there is at
// least one customer to update.
update.setEnabled (false);
// Add a Finish button to the Panel object and register
// the current customer object as a listener for button events.
p.add (b = new Button ("Finish"));
b.addActionListener (this);
// Add the panel object to the frame window container.
add ("South", p);
// Set the background of the frame window container to
// lightGray
setBackground (Color.lightGray);
// Set the size of the frame window container to 400
// pixels horizontally by 200 pixels vertically.
setSize (400, 200);
// Allow the user to resize the frame window.
setResizable (true);
// Load all contacts.
loadCustomers ();
// Make sure that the frame window is visible.
setVisible (true);
public void actionPerformed (ActionEvent e)
if (e.getActionCommand ().equals ("Delete"))
delete ();
else
if (e.getActionCommand ().equals ("Finish"))
saveCustomers ();
System.exit (0);
else
if (e.getActionCommand ().equals ("Insert"))
insert ();
else
update ();
public Insets getInsets ()
// Return an Insets object that describes the number of
// pixels to reserve as a border around the edges of the
// frame window.
return new Insets (10, 10, 10, 10);
public static void main (String [] args)
// Create a new pp object and let it do its thing.
new pp ();
private void delete ()
// Obtain index of selected contact item from the names
// component.
int index = names.getSelectedIndex ();
// If no item was selected, index is -1. We cannot update
// a contact if no contact item in the names component was
// selected - because we would have nothing to work with.
if (index != -1)
// Remove the contact item from the names component.
names.remove (index);
// Remove the Customer object from the contacts Vector
// object.
customers.remove (index);
// If there are no more customers ...
if (customers.size () == 0)
delete.setEnabled (false);
update.setEnabled (false);
else
// Make sure that the first contact item in the names
// list is highlighted.
names.select (0);
private void insert ()
// Create an Insert data entry form to enter information
// for a new customer.
DataEntryForm def = new DataEntryForm (this, "Insert");
// If the bOk Boolean flag is set, this indicates the user
// exited the form by pressing the Ok button.
if (def.bOk)
// Create a Contact object and assign information from
// the form to its fields.
Customer temp = new Customer ();
temp.name = new String (def.name.getText ());
temp.publication = new String (def.publication.getText ());
temp.round = new String (def.round.getText ());
temp.address = new String (def.address.getText ());
temp.phone = new String (def.phone.getText ());
// Add a new customer item to the names component.
names.add (temp.name + ", " + temp.publication);
// Add the Customer object to the contacts Vector
// object.
customers.add (temp);
// Make sure that the Delete and Update buttons are
// enabled.
delete.setEnabled (true);
update.setEnabled (true);
// Destroy the dialouge box.
def.dispose ();
// Make sure that the first customer item in the names list
// is highlighted.
names.select (0);
// ===========================================================
// Load all contacts from contacts.dat into the contacts
// Vector object. Also, make sure that the last name/first
// name from each contact is combined into a String object and
// inserted into the names component - as a contact item.
// ===========================================================
private void loadCustomers ()
FileInputStream fis = null;
try
fis = new FileInputStream ("Customers.dat");
DataInputStream dis = new DataInputStream (fis);
int nCustomers = dis.readInt ();
for (int i = 0; i < nCustomers; i++)
Customer temp = new Customer ();
temp.name = dis.readUTF ();
temp.publication = dis.readUTF ();
temp.round = dis.readUTF ();
temp.address = dis.readUTF ();
temp.phone = dis.readUTF ();
names.add (temp.name + ", " + temp.publication);
customers.add (temp);
if (nCustomers > 0)
delete.setEnabled (true);
update.setEnabled (true);
catch (IOException e)
finally
if (fis != null)
try
fis.close ();
catch (IOException e) {}
// Make sure that the first contact item in the names list
// is highlighted.
names.select (0);
// ========================================================
// Save all Customer objects from the customer Vector object
// to customer.dat. The number of customerss are saved as an
// int to make it easy for loadCustomers () to do its job.
// ========================================================
private void saveCustomers ()
FileOutputStream fos = null;
try
fos = new FileOutputStream ("customers.dat");
DataOutputStream dos = new DataOutputStream (fos);
dos.writeInt (customers.size ());
for (int i = 0; i < customers.size (); i++)
Customer temp = (Customer) customers.elementAt (i);
dos.writeUTF (temp.name);
dos.writeUTF (temp.publication);
dos.writeUTF (temp.round);
dos.writeUTF (temp.address);
dos.writeUTF (temp.phone);
catch (IOException e)
MsgBox mb = new MsgBox (this, "PP Error",
e.toString ());
mb.dispose ();
finally
if (fos != null)
try
fos.close ();
catch (IOException e) {}
private void update ()
// Obtain index of selected customer item from the names
// component.
int index = names.getSelectedIndex ();
// If no item was selected, index is -1. We cannot update
// a customer if no customer item in the names component was
// selected - because we would have nothing to work with.
if (index != -1)
// Obtain a reference to the customer object (from the
// customers Vector object) that is associated with the
// index.
Customer temp = (Customer) customers.elementAt (index);
// Create and display an update entry form.
DataEntryForm def = new DataEntryForm (this, "Update",
temp.name,
temp.publication,
temp.round,
temp.address,
temp.phone);
// If the user pressed Ok...
if (def.bOk)
// Update the customer information in the customers
// Vector object.
temp.name = new String (def.name.getText ());
temp.publication = new String (def.publication.getText ());
temp.round = new String (def.round.getText ());
temp.address = new String (def.address.getText ());
temp.phone = new String (def.phone.getText ());
// Make sure the screen reflects the update.
names.replaceItem (temp.name + ", " + temp.publication,
index);
// Destroy the dialouge box.
def.dispose ();
// Make sure that the first customer item in the names
// list is highlighted.
names.select (0);

Ive doen pretty much what you said burt now my program isnt working at all. The window comes up but instead of doing something when you click the button it just throws shit loads of exceptions. Heres my abridged code
// pp.java
// Grant Brown
// 22/02/02
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
// =========================================================
// Class:PP
// This class drives the Paper Round manager. It contains the
// main method which gets called as soon as this application
// begins to run.
// =========================================================
class pp extends JFrame implements ActionListener
// Container of customer objects (one object per customer)
private Vector customers = new Vector (100);
// List of names component. (Must specify java.awt in
// front of List to distinguish the List class in the
// java.awt package from the List class in the java.util
// package.)
private java.awt.List names = new java.awt.List ();
// Delete and update button components.
private JButton delete;
private JButton update;
// Default constructor.
public pp ()
// Assign Contact Manager to title bar of frame window.
super ("Paper Round Manager");
// Add a listener that responds to window closing
// events. When this event occurs (by clicking on the
// close box in the title bar), save contacts and exit.
addWindowListener (new WindowAdapter ()
public void windowClosing
(WindowEvent e)
saveCustomers ();
System.exit (0);
// Place an empty label in the north part of the frame
// window. This is done to correct an AWT positioning
// problem. (One thing that you'll come to realize as
// you work with the AWT is that there are lots of bugs.)
JLabel l = new JLabel ();
getContentPane().add ("North", l);
// Place the names component in the center part of the
// frame window.
getContentPane().add ("Center", names);
// Create a panel object to hold four buttons.
JPanel p = new JPanel ();
JButton b;
// Add an Insert button to the Panel object and register
// the current cm object as a listener for button events.
p.add (b = new JButton ("Insert"));
b.addActionListener (this);
// Add a Delete button to the Panel object and register
// the current cm object as a listener for button events.
p.add (delete = new JButton ("Delete"));
delete.addActionListener (this);
// The Delete button should be disabled until there is at
// least one contact to delete.
delete.setEnabled (false);
// Add an Update button to the Panel object and register
// the current cm object as a listener for button events.
p.add (update = new JButton ("Update"));
update.addActionListener (this);
// The Update button should be disabled until there is at
// least one contact to update.
update.setEnabled (false);
// Add a Finish button to the Panel object and register
// the current cm object as a listener for button events.
p.add (b = new JButton ("Finish"));
b.addActionListener (this);
// Add the panel object to the frame window container.
getContentPane().add ("South", p);
// Set the background of the frame window container to
// lightGray (to give a pleasing effect).
setBackground (Color.lightGray);
// Set the size of the frame window container to 400
// pixels horizontally by 200 pixels vertically.
setBounds (50, 100, 400, 200);
// Do not allow the user to resize the frame window.
loadCustomers ();
// Load all contacts.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Make sure that the frame window is visible.
setVisible (true);
public void actionPerformed (ActionEvent e)
if (e.getActionCommand ().equals ("Delete"))
delete ();
else
if (e.getActionCommand ().equals ("Finish"))
saveCustomers ();
System.exit (0);
else
if (e.getActionCommand ().equals ("Insert"))
insert ();
else
update ();
public Insets getInsets ()
// Return an Insets object that describes the number of
// pixels to reserve as a border around the edges of the
// frame window.
return new Insets (10, 10, 10, 10);
public static void main (String [] args)
// Create a new cm object and let it do its thing.
new pp ();
private void delete ()
// Obtain index of selected customer item from the names
// component.
int index = names.getSelectedIndex ();
// If no item was selected, index is -1. We cannot update
// a contact if no contact item in the names component was
// selected - because we would have nothing to work with.
if (index != -1)
// Remove the customer item from the names component.
names.remove (index);
// Remove the Customer object from the contacts Vector
// object.
customers.remove (index);
// If there are no more customers ...
if (customers.size () == 0)
delete.setEnabled (false);
update.setEnabled (false);
else
// Make sure that the first contact item in the names
// list is highlighted.
names.select (0);
private void insert ()
// Create an Insert data entry form to enter information
// for a new contact.
DataEntryForm def = new DataEntryForm (this, "Insert");
// If the bOk Boolean flag is set, this indicates the user
// exited the form by pressing the Ok button.
if (def.bOk)
// Create a Customer object and assign information from
// the form to its fields.
Customer temp = new Customer ();
temp.name = new String (def.name.getText ());
temp.publication = new String (def.publication.getText ());
temp.address = new String (def.address.getText ());
temp.round = new String (def.round.getText ());
temp.phone = new String
(def.phone.getText ());
// Add a new customer item to the names component.
names.add (temp.publication + ", " + temp.address);
// Add the Customer object to the contacts Vector
// object.
customers.add (temp);
// Make sure that the Delete and Update buttons are
// enabled.
delete.setEnabled (true);
update.setEnabled (true);
// Destroy the dialog box.
def.dispose ();
// Make sure that the first customer item in the names list
// is highlighted.
names.select (0);
// ===========================================================
// Load all customers from customers.dat into the customers
// Vector object. Also, make sure that the last name/first
// name from each contact is combined into a String object and
// inserted into the names component - as a contact item.
// ===========================================================
private void loadCustomers ()
FileInputStream fis = null;
try
fis = new FileInputStream ("customers.dat");
DataInputStream dis = new DataInputStream (fis);
int nCustomers = dis.readInt ();
for (int i = 0; i < nCustomers; i++)
Customer temp = new Customer ();
temp.name = dis.readUTF ();
temp.publication = dis.readUTF ();
temp.address = dis.readUTF ();
temp.round = dis.readUTF ();
temp.phone = dis.readUTF ();
names.add (temp.publication + ", " + temp.address);
customers.add (temp);
if (nCustomers > 0)
delete.setEnabled (true);
update.setEnabled (true);
catch (IOException e)
finally
if (fis != null)
try
fis.close ();
catch (IOException e) {}
// Make sure that the first customer item in the names list
// is highlighted.
names.select (0);
// ========================================================
// Save all customer objects from the contacts Vector object
// to customers.dat. The number of contacts are saved as an
// int to make it easy for loadCustomers () to do its job.
// ========================================================
private void saveCustomers ()
FileOutputStream fos = null;
try
fos = new FileOutputStream ("customers.dat");
DataOutputStream dos = new DataOutputStream (fos);
dos.writeInt (customers.size ());
for (int i = 0; i < customers.size (); i++)
Customer temp = (Customer) customers.elementAt (i);
dos.writeUTF (temp.name);
dos.writeUTF (temp.publication);
dos.writeUTF (temp.address);
dos.writeUTF (temp.round);
dos.writeUTF (temp.phone);
catch (IOException e)
MsgBox mb = new MsgBox (this, "PP Error",
e.toString ());
mb.dispose ();
finally
if (fos != null)
try
fos.close ();
catch (IOException e) {}
private void update ()
// Obtain index of selected customer item from the names
// component.
int index = names.getSelectedIndex ();
// If no item was selected, index is -1. We cannot update
// a customer if no customer item in the names component was
// selected - because we would have nothing to work with.
if (index != -1)
// Obtain a reference to the Customer object (from the
// customer Vector object) that is associated with the
// index.
Customer temp = (Customer) customers.elementAt (index);
// Create and display an update entry form.
DataEntryForm def = new DataEntryForm (this, "Update",
temp.name,
temp.publication,
temp.address,
temp.round,
temp.phone);
// If the user pressed Ok...
if (def.bOk)
// Update the customer information in the customers
// Vector object.
temp.name = new String (def.name.getText ());
temp.publication = new String (def.publication.getText ());
temp.address = new String (def.address.getText ());
temp.round = new String (def.round.getText ());
temp.phone = new String (def.phone.getText ());
// Make sure the screen reflects the update.
names.replaceItem (temp.publication + ", " + temp.address,
index);
// Destroy the dialog box.
def.dispose ();
// Make sure that the first customer item in the names
// list is highlighted.
names.select (0);
// ========================================================
// Class: Customer
// This class describes the contents of a business customer.
// ========================================================
class Customer
public String name;
public String publication;
public String address;
public String round;
public String phone;
// ==========================================================
// Class: DataEntryForm
// This class provides a data entry form for entering customer
// information.
// ==========================================================
class DataEntryForm extends JDialog implements ActionListener
// bOk is a boolean flag. When true, it indicates that
// the Ok button was pressed to terminate the dialog box
// (as opposed to the Cancel button).
public boolean bOk;
// The following components hold the text that the user
// entered into the visible text fields.
public JTextField name;
public JTextField publication;
public JTextField address;
public JTextField round;
public JTextField phone;
public void actionPerformed (ActionEvent e)
// If the user pressed the Ok button, indicate this
// by assigning true to bOk.
if (e.getActionCommand ().equals ("Ok"))
bOk = true;
// Destroy the dialog box and return to the point
// just after the creation of the DataEntryForm object.
dispose ();
public DataEntryForm (JFrame parent, String title)
// Call the other constructor. The current constructor
// is used for insert operations. The other constructor
// is used for update operations.
this (parent, title, "", "", "", "", "");
public DataEntryForm (JFrame parent, String title,
String name, String publication,
String address, String round,
String phone)
// Initialize the superclass layer.
super (parent, title, true);
// Choose a grid bag layout so that components can be more
// accurately positioned. (It looks nicer.)
setLayout (new GridBagLayout ());
// Add appropriate first name, last name, phone, fax, and
// email components to the current DataEntryForm container.
// (Remember, DataEntryForm is a subclass of Dialog.
// Dialog is a container. Therefore, DataEntryForm
// inherits the ability to be a container.)
addComponent (this, new JLabel ("Name: "), 0, 0, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.WEST);
this.name = new JTextField (15);
addComponent (this, this.name, 1, 0, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
if (title.equals ("Update"))
this.name.setText (name);
addComponent (this, new JLabel ("Publications: "), 0, 1, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.WEST);
this.publication = new JTextField (15);
addComponent (this, this.publication, 1, 1, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
if (title.equals ("Update"))
this.publication.setText (publication);
addComponent (this, new JLabel ("Address "), 0, 2, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.WEST);
this.address = new JTextField (15);
addComponent (this, this.address, 1, 2, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
if (title.equals ("Update"))
this.address.setText (address);
addComponent (this, new JLabel ("Round No "), 0, 3, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.WEST);
this.round = new JTextField (15);
addComponent (this, this.round, 1, 3, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
if (title.equals ("Update"))
this.round.setText (round);
addComponent (this, new JLabel ("Phone Number "), 0, 4, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.WEST);
this.phone = new JTextField (15);
addComponent (this, this.phone, 1, 4, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
if (title.equals ("Update"))
this.phone.setText (phone);
addComponent (this, new JLabel (""), 0, 5, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
addComponent (this, new JLabel (""), 1, 5, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
JButton b;
// Add an Ok button to this container.
addComponent (this, b = new JButton ("Ok"), 0, 6, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
b.addActionListener (this);
// Add a Cancel button to this container.
addComponent (this, b = new JButton ("Cancel"), 1, 6, 1, 1,
GridBagConstraints.NONE,
GridBagConstraints.CENTER);
b.addActionListener (this);
// Set the size of the dialog window to 250 pixels
// horizontally by 200 pixels vertically.
setSize (250, 200);
// Do not allow users to resize the dialog window.
setResizable (false);
// Make sure that the dialog window is visible.
setVisible (true);
private void addComponent (Container con, Component com,
int gridx, int gridy,
int gridw, int gridh, int fill,
int anchor)
// Get the current layout manager. It is assumed to
// be a GridBagLayout object.
LayoutManager lm = con.getLayout ();
// Create a GridBagConstraints object to make it
// possible to customize component positioning.
GridBagConstraints gbc = new GridBagConstraints ();
// Assign the x and y grid positions.
gbc.gridx = gridx;
gbc.gridy = gridy;
// Assign the number of grid blocks horizontally and
// vertically that are occupied by the component.
gbc.gridwidth = gridw;
gbc.gridheight = gridh;
// Specify the component's resize policy (fill) and
// the direction in which the component is positioned
// when its size is smaller than available space (anchor).
gbc.fill = fill;
gbc.anchor = anchor;
// Set the new constraints that the grid bag layout
// manager will use.
((GridBagLayout) lm).setConstraints (com, gbc);
// Add the component to the container.
con.add (com);
// ===========================================================
// Class: MsgBox
// This class displays a message box to the user. The message
// is usually an error message. The user must press the Ok
// button to terminate the message box.
// ===========================================================
class MsgBox extends JDialog implements ActionListener
public void actionPerformed (ActionEvent e)
// Terminate the dialog box in response to the user
// pressing the Ok button.
dispose ();
public MsgBox (JFrame parent, String title, String msg)
// Initialize the superclass layer.
super (parent, title, true);
// Store the msg argument in a Label object and add
// this object to the center part of the dialog window.
JLabel l = new JLabel (msg);
add ("Center", l);
// Create a Button object and add it to the south part
// of the dialog window.
JButton b = new JButton ("Ok");
add ("South", b);
// Make the current object a listener to events that
// occur as a result of the user pressing the Ok
// button.
b.addActionListener (this);
// Make sure that the Ok button has the focus.
b.requestFocus ();
// Do not allow users to resize the dialog window.
setResizable (false);
// Allow the layout manager to choose an appropriate
// size for the dialog window.
pack ();
// Make sure that the dialog window is visible.
setVisible (true);
}

AWT vs SWING and more

1)Though the components used in awt and swing are similar what is the need for two seperate packages ?
and
2)what is the main usage of "getContentPane()" ?
3)why do we use an appletviewer for executing applets provided the OS is Windows NT ..

1)Though the components used in awt and swing are
similar what is the need for two seperate packages ?AWT uses the native (heavyweight) components of the underlying Operating System. Actually a common (and small) subset of the provided components.
In Swing the components a lightweight, there's no native component behind them, the components are painted by pure java code (sometimes sophisticated components). The swing applications thus can look and feel the same on all platforms.
2)what is the main usage of "getContentPane()" ?When using swing you shouldn't add lightweight components to the window subclasses, only to the content pane.
3)why do we use an appletviewer for executing applets
provided the OS is Windows NT ..Did not understand.
Kurta

Difference between awt ang Swing Interview Question n other Question

hi every one i use to think that i know java atlest so much that i can crack a lolcal comp interview but ........................
i ansered few Question but was speachlees when was asked few of this i do not remember all of them
1] difference between awt and swing.
2]System.out.println();
System is a class out is a variable so who come a variable calling a method.
3]are constractor inherateed in java.

1] difference between awt and swing.AWT is based on an abstraction of platform-specific, heavy-weight components. Swing is written entirely in java.
>
2]System.out.println();
System is a class out is a variable so who come a
variable calling a method.Do you mean how come?
In that case, the answer is simple: Because out is a variable, it can be redirected/compared against, etc much easier
3]are constractor inherateed in java.Kind of a trick question, as the answer is yes and no. Constructors are not inherited, but every constructor in the subclass must call one and exactly one constructor of the superclass

Why the AWT components are called heavy-weight and SWING as light-weight?

Why the AWT components are called heavy-weight and SWING as light-weight?.
Building our own components means overhead on JVM. hence in what sence the SWING components are called light weight.?
I know that the Swing componets are the components which are not going to depend upon peer classes and render, OS independent LOOK n FEEL.
Thanks,
Sanath Kumar

All extensions of Component are considered lightweight since, as you point out, they don't have their own dedicated native peer.
Essentially a lightweight component only has a canvas on which to draw itself and some means of receiving events from the system. In fact, there is no need to have one of these "canvas" and "event" objects for each component - the parent component can manage these abilities on behalf of its children. Eventually you end up with only top-level components needing to be heavyweight in order to communicate with the windowing system.
A lightweight component therefore has the minimal dependency on the underlying windowing system giving you maximum cross-platform flexibility.
It is usually true that lightweight => slower and heavyweight => faster since it is reasonable to assume that native peers will be optimal for the windowing system. However, that's not the point of the lightweight/heavyweight distinction.
Hope this helps.

Why to need close the result set and statement

why to need close the result set and statement

It's best to explicitly close every ResultSet, Statement, and Connection in the narrowest scope possible.
These should be closed in a finally block.
Since each close() method throws SQLException, each one should be in an individual try/catch block to ensure that a failure to close one won't ruin the chances for all the others.
You can capture this in one nice utility class, like this:
package db;
import java.sql.*;
import java.util.ArrayList;
import java.util.Map;
import java.util.LinkedHashMap;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
* Created by IntelliJ IDEA.
* User: MD87020
* Date: Feb 16, 2005
* Time: 8:42:19 PM
* To change this template use File | Settings | File Templates.
public class DatabaseUtils
     * Logger for DatabaseUtils
    private static final Log logger = LogFactory.getLog(DatabaseUtils.class);
    /** Private default ctor to prevent subclassing and instantiation */
    private DatabaseUtils() {}
     * Close a connection
     * @param connection to close
    public static void close(Connection connection)
        try
            if ((connection != null) && !connection.isClosed())
                connection.close();
        catch (SQLException e)
            logger.error("Could not close connection", e);
     * Close a statement
     * @param statement to close
    public static void close(Statement statement)
        try
            if (statement != null)
                statement.close();
        catch (SQLException e)
            logger.error("Could not close statement", e);
     * Close a result set
     * @param rs to close
    public static void close(ResultSet rs)
        try
            if (rs != null)
                rs.close();
        catch (SQLException e)
            logger.error("Could not close result set", e);
     * Close both a connection and statement
     * @param connection to close
     * @param statement to close
    public static void close(Connection connection, Statement statement)
        close(statement);
        close(connection);
     * Close a connection, statement, and result set
     * @param connection to close
     * @param statement to close
     * @param rs to close
    public static void close(Connection connection,
                             Statement statement,
                             ResultSet rs)
        close(rs);
        close(statement);
        close(connection);
     * Helper method that maps a ResultSet into a map of columns
     * @param rs ResultSet
     * @return map of lists, one per column, with column name as the key
     * @throws SQLException if the connection fails
    public static final Map toMap(ResultSet rs) throws SQLException
        List wantedColumnNames = getColumnNames(rs);
        return toMap(rs, wantedColumnNames);
     * Helper method that maps a ResultSet into a map of column lists
     * @param rs ResultSet
     * @param wantedColumnNames of columns names to include in the result map
     * @return map of lists, one per column, with column name as the key
     * @throws SQLException if the connection fails
    public static final Map toMap(ResultSet rs, List wantedColumnNames)
        throws SQLException
        // Set up the map of columns
        int numWantedColumns    = wantedColumnNames.size();
        Map columns             = new LinkedHashMap(numWantedColumns);
        for (int i = 0; i < numWantedColumns; ++i)
            List columnValues   = new ArrayList();
            columns.put(wantedColumnNames.get(i), columnValues);
        while (rs.next())
            for (int i = 0; i < numWantedColumns; ++i)
                String columnName   = (String)wantedColumnNames.get(i);
                Object value        = rs.getObject(columnName);
                List columnValues   = (List)columns.get(columnName);
                columnValues.add(value);
                columns.put(columnName, columnValues);
        return columns;
     * Helper method that converts a ResultSet into a list of maps, one per row
     * @param rs ResultSet
     * @return list of maps, one per row, with column name as the key
     * @throws SQLException if the connection fails
    public static final List toList(ResultSet rs) throws SQLException
        List wantedColumnNames = getColumnNames(rs);
        return toList(rs, wantedColumnNames);
     * Helper method that maps a ResultSet into a list of maps, one per row
     * @param rs ResultSet
     * @param wantedColumnNames of columns names to include in the result map
     * @return list of maps, one per column row, with column names as keys
     * @throws SQLException if the connection fails
    public static final List toList(ResultSet rs, List wantedColumnNames)
        throws SQLException
        List rows = new ArrayList();
        int numWantedColumns = wantedColumnNames.size();
        while (rs.next())
            Map row = new LinkedHashMap();
            for (int i = 0; i < numWantedColumns; ++i)
                String columnName   = (String)wantedColumnNames.get(i);
                Object value = rs.getObject(columnName);
                row.put(columnName, value);
            rows.add(row);
        return rows;
      * Return all column names as a list of strings
      * @param rs query result set
      * @return list of column name strings
      * @throws SQLException if the query fails
    public static final List getColumnNames(ResultSet rs) throws SQLException
        ResultSetMetaData meta = rs.getMetaData();
        int numColumns = meta.getColumnCount();
        List columnNames = new ArrayList(numColumns);
        for (int i = 1; i <= numColumns; ++i)
            columnNames.add(meta.getColumnName(i));
        return columnNames;
}Anybody who lets the GC or timeouts or sheer luck handle their resource recovery for them is a hack and gets what they deserve.
Do a search on problems with Oracle cursors being exhausted and learn what the root cause is. That should convince you.
scsi-boy is 100% correct.
%

Why don't lyrics support hard returns and left justification?

When I copy and paste lyrics into the lyrics field everything looks fine. But when I sync on my iPhone, suddenly they are centered on the screen and they seem to have lost the hard returns. Is there anyway to fix this?
Thanks!

Programmers have changed the world only because they don't think,
Leave it the way it is!Don't mind..
If java 'did this for you' then teachers of the
language, such as myself, would lose the opportunity
to instruct newbies on some very important concepts
early in the program.I can't agree with this with a reason,
when started learning Java i was already knowing C and C++.
So the path i follwed for learning was C--> C++ --> Java.
So it doesn't become as such difficult to learn Java.
Nowadays when a student come to class he wants to learn Java Directly,
And that's the point where all problem is,
Serveral students ask me If we can use System.out.println() to print to console ?? What is for input??
Because the new commer is not going to start with awt Or Swings directly??
why not to have simple support fot input??
All people here are advicing to use a class file designed for Input, So my question is why Java itself don't provide such Class in JDK itself??
Isn't it a basic need ??
I know that java is not made console application ?
Buf for convinience can't they add this feature (e.g. we have Adapter classes, they are also for cnvinience, right?? )
Any views are appriciated..
--Bhupendra Mahajan

Been sat here for the past 5 hours trying to figure out why itunes wont download, it says error and something to do with Microsoft? Help me please.. getting a bit bored?

been sat here for the past 5 hours trying to figure out why itunes wont download, it says error and something to do with Microsoft version? Help me please.. getting a bit bored?

i have this problem too
my dad thinks its because itunes is getting overloaded

Since iOS 7.1 my phone won't turn on and is asking me to connect to iTunes. I connect to itunes and it says it needs to be restored. Not sure why. I try to restore it and then it says something went wrong and it won't work. So I've been without my phone

Since iOS 7.1 my phone won't turn on and is asking me to connect to iTunes. I connect to itunes and it says it needs to be restored. Not sure why. I try to restore it and then it says something went wrong and it won't work. So I've been without my phone for a couple days now. It gives me error code (29). The phone almost reboots and then 3/4 of the way through it gives me the error message.

If using windows...
Temporarily disable your firewall and antivirus software and try again...
http://support.apple.com/kb/TS1379
See iTunes Connection Issues here...
iTunes for Windows: Troubleshooting security software issues
NOTE:
Make sure you have the Latest Version of iTunes (v11.1.5) Installed on your computer
iTunes free download from www.itunes.com/download

The display on my iPod is extra large and I am have no idea why. I tried the HOME button and the power button at the same time but that doesn't work. I can't even enter my code to unlock it because I cannot scroll the HUGE display! Any ideas??

The display on my iPod Touch is HUGE and I have no idea why. I tried the HOME button and power button at the same time.....no help. I cannot enter my unlock code because I can't scroll without entering a wrong number! HELP!!

Using three fingers, double-tap the screen.
http://support.apple.com/kb/TS3129

Why is iMessage taking my incoming emails and then not making them available for my PC to get? Why can I not send a text msg with photos when iMessage is turned off (but MMS is still on).

Apple is great!
Why is iMessage taking my incoming emails and then not making them available for my PC to get? Why can I not send a text msg with photos when iMessage is turned off (but MMS is still on).
I compose an iMessage with the destination as my email address and I attach 2 photos I want on my PC. I send them several times from my iPhone 5C but they never arrive. I look at my ipad later and realize that it's iMessage app is getting ( and swallowing) these emails. I then turn the ipad off. Still can't get the photos through because iphone is now getting them on it's iMessage. I turn off the iMessage feature and try to send photos from text msging. Phone tells me it can't send photos unless iMessage it turned on. What happened to regular MMS text messaging? I go and try to send photos as an email attachment and see that there is no option to attach from the stupid email program. I look up online to learn about the brave new world of apple attachments and send them.
Why is iMessage taking my incoming emails and then not making them available for my PC to get?
The email program on my iphone is not configured to remove messages from the server.
If iMessage is turned off I don't have the issue.
Why can I not send a text msg with photos when iMessage is turned off (but MMS is still on).

Did not work. I've selected iMessage to ON and left it. After a few hours I recieved a message "activation unsuccessful. Turn on iMessage to try again". This has been going on for the past 3 days.

Why does closing all open windows (15) and leaving only one drop ram usage from 1.5 to 1.4Gb and not more.

Why does closing all open windows (15) and leaving only one drop ram usage by only 100mb from 1.5 to 1.4Gb.
What is in this 1.4 gb ?
I don't care much about ram, It's just that cpu usage spike like crazy by the end.
''Edited to remove swearing - TonyE''

Hi musicfan,<br />Sorry you are having problems with Firefox. Maybe you should have asked earlier and we could have fixed it.
Reading your comments I do not see that rolling back to an insecure Firefox 22 will actually help you much. You are probably best using IE, unless you have also damaged that.
*[[Export bookmarks to Internet Explorer]]
You should not use old versions they are insecure. Security fixes are publicised and exploitable.
* [[Install an older version of Firefox]]
* https://www.mozilla.org/security/known-vulnerabilities/firefox.html
Most others will not be having such problems. We are now able to say that with confidence because after developers missed a regression in Firefox 4 telemetry was introduced so that data was obtained. It may be an idea to turn on your telemetry, if you have not already done so, and decide to stick with Firefox.
*[[Send performance data to Mozilla to help improve Firefox]]
Trying safe mode takes seconds. Unfortunatly if you are not willing to do even rudimentary troubleshooting there is not anything we can do to help you.
*[[Troubleshoot Firefox issues using Safe Mode]]

Where is "cut" command in Mac? Why I cannot cut a file/folder and paste it somewhere else?

I'm a professioinal who made the big step to pass from Windows to Mac. I do not regret it but there're things I cannot understand and i supposed being much easier or "native" in Mac.
Tipical example is the Cut command. I see it in Finder but why doesn't if work? Drag and drop do not copy but works like a ct and paste! I think if for mac this is enough Apple is gonna make it work bacause is a HUGE limit, specially for people like me who manage thousands of photos and cannot risk to drop huge amounts of files in a go or in a wrong folder of such.
Please tell me I'm wrong and there's a way to sort it out!
Thanks.
D

You can cut and paste items with Finder, a new feature in Lion, but it doesn't use the command-X "cut" command and is not very intuitive.
Highlight the item(s) to be moved, and type command-C to copy it. Then navigate to the destination window, and rather than pressing command-V (or Edit>Paste item) , instead press Option-command-V (or hold down option when using the Edit menu). This changes "paste" into "move item here", i.e, the item will disappear from where it was copied. The result is equivalent to a "cut and paste."

Why is HeadlessException explicitly thrown in AWT and swing?

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