code: public int put(Widget widget) {
  		attach(widget);
  		for (int i = 0; i < content.length; ++i)
  			for (int j = 0; j < content[i].length; ++j)
  				if (content[i][j] == null) {
  					content[i][j] = widget;
  					this.sendElement();
  					return i;
  				}
  		throw new IndexOutOfBoundsException();
  		//return -1;
  	}
docs: Puts widget at first free index
  
  @param widget Widget to put
  @return index of element in container