Get JFrame size

Source code below will create a JFrame with a button in it. You can know current JFrame size by click the button. You also can try resize the JFrame first, and after that click the button.

*****************************************************************************
COMPLETE SOURCE CODE FOR : GetJFrameSize.java
*****************************************************************************

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

import java.awt.FlowLayout;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class GetJFrameSize extends JFrame
{
//Create ActionListener for listen when someone click button
ActionListener al=new ActionListener()
{
 //Overwrite abstract method ( actionPerformed ) in ActionListener class
 public void actionPerformed(ActionEvent event)
 {
  //Show message box that contain information about current JFrame width and height in pixels
  JOptionPane.showMessageDialog(null,"JFrame size in pixels is : \n"+"WIDTH : "+getSize().width+"\n"+"HEIGHT : "+getSize().height);
 }
};

public GetJFrameSize()
{
 //Create JFrame title ( Resize me and click button )
 super("Resize me and click button");

 //Set JFrame layout to FlowLayout
 setLayout(new FlowLayout());

 //Create a button with text ( Click me to see current JFrame size )
 JButton button=new JButton("Click me to see current JFrame size");

 //Add ActionListener to the button
 button.addActionListener(al);

 //Add the button into created JFrame
 add(button);

 //Set default close operation for JFrame
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set initial JFrame size to :
 //WIDTH = 500 pixels
 //HEIGHT = 500 pixels
 setSize(500,500);

 //Make JFrame visible
 setVisible(true);
}

public static void main(String[]args)
{
 GetJFrameSize gjfs=new GetJFrameSize();
}
}

*****************************************************************************
JUST COMPILE AND EXECUTE IT
*****************************************************************************