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COMPLETE SOURCE CODE FOR : FullScreenInJava2.java
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import java.awt.Frame;
import java.awt.Button;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.FlowLayout;
public class FullScreenInJava2
{
 public static void main(String[]args)
 {
  Frame a=new Frame();
  Button b=new Button("CLICK HERE TO DISABLE FULL SCREEN");
  
  ActionListener al=new ActionListener()
  {
   public void actionPerformed(ActionEvent evt)
   {
    System.exit(0);
   } 
  };
  
  b.addActionListener(al);
  
  a.setLayout(new FlowLayout());
  a.add(b);
  
  a.setSize((Toolkit.getDefaultToolkit().getScreenSize()).width,(Toolkit.getDefaultToolkit().getScreenSize()).height);
  a.setUndecorated(true);
  a.setAlwaysOnTop(true);
  a.setVisible(true);
 }
}
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JUST COMPILE AND EXECUTE IT
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