code: public void setOpacity(double opacity) {
  		getLayerInfo().setStyle(Double.toString(opacity));
  		handlerManager.fireEvent(new LayerStyleChangeEvent(this));
  	}
docs: Apply a new opacity on the entire raster layer.
  
  @param opacity The new opacity value. Must be a value between 0 and 1, where 0 means invisible and 1 is totally
  visible.
  @since 1.8.0