ImageIcon image = new ImageIcon( "myIcon.png" );
myFrame.setIconImage( image.getImage() );
fenster.setIconImage(new ImageIcon(this.getClass().getResource ("pfadZuDeinemIconFuerObenLinks")).getImage());
this.setIcon (new ImageIcon(this.getClass().getResource ("Pfad/Zu/PNG/in/Jar.png")).getImage());