import java.awt.*;
 
public class ventana extends Window {
 
GraphicsDevice myDevice;
 
	public ventana (){
 
		super(new Frame());	
		try{myDevice.setFullScreenWindow(this);}catch(Exception e){System.out.println(e);}
		setVisible(true);
	}
 
	public static void main(String args[]){
 
		new ventana();
	}
}

java.lang.NullPointerException

import java.awt.*;
 
public class ventana extends Window {
	private static final long serialVersionUID = 1L;
    GraphicsDevice myDevice;
	public ventana (){
 
		super(new Frame());	
		try{
			GraphicsEnvironment environment=GraphicsEnvironment.getLocalGraphicsEnvironment();
			myDevice = environment.getDefaultScreenDevice();
			myDevice.setFullScreenWindow(this);
 
			}catch(Exception e){System.err.println(e);}
		setVisible(true);
	}
	public static void main(String args[]){
		new ventana();
	}
}