asked on

java Class FAQ

i have a java program like below:

import java.sql.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class popUp extends JPanel implements ActionListener
{
      public popUp()
      {
            System.out.println("popUp");
      }

      public static void main(String[] args)
      {
            new popUp().createComponents();
      }
}

i have i question that is y i didn't call the popUp function but the popUp function will call by itself?

thanks

Kennywen

ASKER

if i use:

javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createComponents();
}
});

then the popUp will not run by itself ... why?

thanks

concon

Hi Kennywen,

popUp() is the constructor of the class. and if your create new instance of class it runs.

also you can not call a non-static method from a static method. so you need to create an instance of popUp class in order to call another method from main.

Regards.

Mayank S

I don't understand your question properly.

Kennywen

ASKER

i mean the new popUp().createComponents(); will call the public popUp() function rite?

Mayank S

It should.

Kennywen

ASKER

javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createComponents();
}
});

what is the above function???

Mayank S

It causes the run() to be executed asynchronously on the AWT event dispatching thread. This will happen after all pending AWT events have been processed. This method should be used when an application thread needs to update the GUI.

Where are you writing that invokeLater () code?

Kennywen

ASKER

in main method.

Mayank S

You mean:

public static void main ( String args[] )
{
SwingUtitlies.invokeLater ( .... ) ;

}

??

That will obviously not call popUp ().

Kennywen

ASKER

sorry, why the SwingUtitlies.invokeLater ( .... ) ; will not call popUp ()?

thanks

SOLUTION

concon

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Mayank S

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Kennywen

ASKER

thank you and forgive my poor english.

Mayank S

Glad to help ;-)

Kennywen

ASKER

those method that call by the main method must be static rite?

is there anyway to create a non-static method from the main method without create an instance of it?

thanks

Mayank S

No. You need to make an object to call the non-static method. Otherwise, you will not be able to do it.

The reason why you were able to call createComponents from main () was that your main () is in the popUp class. Try putting the main () separately in a different class and use the same SwingUtilities.invokeLater () code - I don't think that it'll compile.

Kennywen

ASKER

thanks again