Draw line in JFrame

Source code below will draw a line from top left corner of a JFrame until bottom right corner of the JFrame.

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COMPLETE SOURCE CODE FOR : DrawLineInJFrame.java
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import javax.swing.JFrame;

import java.awt.Graphics;

public class DrawLineInJFrame extends JFrame
{
public DrawLineInJFrame()
{
 //Set JFrame title
 super("Draw A Line In JFrame");

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

 //Set JFrame size
 setSize(400,400);

 //Make JFrame visible 
 setVisible(true);
}

public void paint(Graphics g)
{
 super.paint(g);

 //draw line in JFrame from top left corner until bottom right corner
 g.drawLine(0,0,getSize().width,getSize().height);
}

public static void main(String[]args)
{
 DrawLineInJFrame dlijf=new DrawLineInJFrame();
}
}

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JUST COMPILE AND EXECUTE IT
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