What is wrong with this simple code?

[venandane]

Hi all,

This simple code was taken from "Java how to program 9th ed". I don't understand why the output is printed twice. Someone please shed some light....

Alvin


// Demonstrates a problem
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;

public class Problem extends JPanel
{
public void paintComponent( Graphics g )
{
super.paintComponent( g );

Color c = new Color(241, 40, 50);

System.out.println("This line is output twice! What am I doing wrong? (example taken from Java how to program 9th ed)");

// draw ring
g.setColor( c );
g.fillOval( 10, 10, 200, 200 );

} // end method paintComponent
} // end class Problem


The code below is the main method to call the above Class "Problem"

// Test class problem
import javax.swing.JFrame;

public class ProblemTest
{
public static void main( String[] args )
{
Problem panel = new Problem();
JFrame application = new JFrame();

application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
application.add( panel );
application.setSize( 250, 250 );
application.setVisible( true );
} // end main
} // end class ProblemTest

[kkji]

are you able to compile the file?

[venandane]

Its compiles and run fine. Just that its running the for loop twice. I guess the paintcomponent method is being called from somewhere...

[doWhile]

Its compiles and run fine. Just that its running the for loop twice. I guess the paintcomponent method is being called from somewhere...

What makes you think this is incorrect behavior?

[Cosmos]

you are calling paintComponent.....

i was having the same problem few days back.....you dont have a control over paint methods......they will be called whenever there is a need to paint the screen again....

try to change the dimension of the appletviewer screen....you will get to know that you really dont have a control over calling of paint method......paint will simply be called when java thinks there is a need to reapaint the screen with the new content.....